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Atari Online News, Etc. Volume 11 Issue 30
Volume 11, Issue 30 Atari Online News, Etc. July 24, 2009
Published and Copyright (c) 1999 - 2008
All Rights Reserved
Atari Online News, Etc.
A-ONE Online Magazine
Dana P. Jacobson, Publisher/Managing Editor
Joseph Mirando, Managing Editor
Rob Mahlert, Associate Editor
Atari Online News, Etc. Staff
Dana P. Jacobson -- Editor
Joe Mirando -- "People Are Talking"
Michael Burkley -- "Unabashed Atariophile"
Albert Dayes -- "CC: Classic Chips"
Rob Mahlert -- Web site
Thomas J. Andrews -- "Keeper of the Flame"
With Contributions by:
Fred Horvat
To subscribe to A-ONE, change e-mail addresses, or unsubscribe,
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=~=~=~=
A-ONE #1130 07/24/09
~ Win 7 to Manufacturing ~ People Are Talking! ~ Laptop Prices Dip!
~ The Ultimate C64 Talk! ~ Wal-Mart: More Laptops ~ Wii Sports Resort!
~ Upgrade Paths to in 7! ~ ~ Games on Demand!
-* A Shortage of Cyber Experts! *-
-* AOL Tries To Recapture Its 'Youth'! *-
-* Microsoft/EU Trying To Settle Browser Case *-
=~=~=~=
->From the Editor's Keyboard "Saying it like it is!"
""""""""""""""""""""""""""
Another LONG week - this is getting wearisome! The weather has been doing
an incredible flip-flop this week - sunny and "warm" for a couple of days,
and rainy and cooler the rest. No Spring, no Summer...yet. Very unusual
weather patterns this year - and I'm not too happy about that! However,
there isn't a damn thing that we can do about it.
Lots of things in the political spotlight lately, but frankly, I'm not
feeling up to debating those issues. After all, what would be the point?
I have my views, you have yours, and the politicians are going to do what
they want to do regardless of how you and I feel!
So, instead of my debating the issues and making myself crazy, I think I'll
just move on to this week's issue. Even the interesting technology stories
have been dwindling over the past few weeks, but we'll take what we can!
Until next time...
=~=~=~=
PEOPLE ARE TALKING
compiled by Joe Mirando
joe@atarinews.org
Hidi ho friends and neighbors. Another week has come and gone, and things are
no better with UseNet access for me. This week, I'll be using Google Groups
(formerly DejaNews.Com), but I'm really not crazy about the way it's set
up. If you have any thoughts/ideas/opinions/options, please let me know.
Hmmm... what to talk about this week. Health care? Nah. We did that last
week. The problem with talking about health care is that everyone is
talking about something different. I said it last week and I'll say it
again this week... we don't need health care reform. We've got the best,
most widely available health care in the world. What we need is health
care INSURANCE reform.
I think I've about beat that one to the ground for now, no? Let's see...
other topics, other topics. The sad state of UseNet access? Nah. Covered
that. Oh! How about the weather?
It's been really screwy here in the northeast lately. This is the middle
of the summer and we should be having some hot, humid days. But so far,
it's been well below average temp-wise. It's also been rainy. The most
rainy July _I_ can remember for a July.
Of course, since the temperatures have been below normal, you get those
idiots who discount the possibility of global warming whining and/or
complaining. The fact is that things ARE changing. I tend to think that
the human race IS affecting the environment, but even if we're not, the
environment IS changing. Ice caps and glaciers are melting, the oceans
are warming, weather patterns changing.
I don't give a tinker's damn WHY they're changing. They ARE. It's not
going to matter why things are changing if the American great plains
become desert and they start growing summer wheat in January in
Manitoba. We'd still be in dire straights.
And don't make the mistake of taking the "Save the Planet" stance either.
Let's be very clear: The Earth has been here for quite a while. Whether
we humans survive as a race or not will make little difference to old
Mother Earth. We could, in fact, destroy every living thing on the planet
and Mother Earth would still be here. She can afford to wait. When the
time is right again, she'll start with whatever she 'decides' to put
forth. It is US who would be but a memory, if that, in the long history
of the Earth.
Well, enough of that. Let's get to the news, hints, tips and info
available from the UseNet.
From the comp.sys.atari.st NewsGroup
====================================
I think we covered some of this before, but there's some interesting stuff
here, and not much else in the NewsGroup this week, so bear with me, okay?
Phantom asks about projects for the STacy:
"In my spare time, I've been upgrading a STacy Laptop. Anyone else working
on one that want to exchange info/ideas?
[I'm] Currently looking for info on what others have done in upgrading
the performance/etc, of this machine."
Jo Even Skarstein replies:
"I clocked it at 12Mhz. The only thing I had to do was to feed the ACIAs
with 500kHz and the floppy controller with 2Mhz. It doesn't work with an
external monitor connected though.
If I still had a Stacy I would upgrade it to 4Mb, add an IDE interface
and replace the HD with a CF-card. Then I would leave it alone. [grin]"
Phantom asks Jo Even:
"What type of IDE interface? Where can I get one?
Did yours have a Bus Connector? My board has a place for one, is it as
easy as soldering in the Bus connector or are there more components that
would need installing?
If I remember correctly, the Bus connector, suppose to be similar to the
Mega ST Bus?
Jo Even replies:
"Nowadays I think you have to build one yourself... Another option would
be a SatanDisk connected to the internal ACSI-connector. Then you can
get rid of the ancient SCSI-disk and the SCSI interface.
You can also replace the EL backlight with a reflective sheet and some
LEDs. If you do this you get rid of the two major power consumers in
the Stacy - the disk and the backlight. Fitting a battery might make
sense now.
I had an ICD AdSpeed16 in one of my Stacys. It worked fine.
A tip when removing the old 68000: Cut all the legs, then desolder each
leg individually. If you don't do this, there's a good chance that
you'll lift or damage some tracks on the motherboard.
Guillaume Tello adds:
"I really would be interested in such projects! Upgrading the STACY to
4Mb (I have seen a web page) looks a bit hard for me: the guy says that
you have to unsolder the previous ram chips. But something to change the
LCD screen would be great!"
Phantom explains what he'd like:
"The one I have already has the 4 megs. (from Factory)
I have a switchable 8/16mhz 68000 board (Fast Technologies),
that I plan on installing if it will work. Have to desolder the
original 68000 chip. Before I do that, anyone know if there
would be a problem running it at 16mhz?
Changing out the LCD to something better would be nice.
And if one could get some type of graphics card to work in
there...."
Guillaume tells Phantom:
"Not sure about having to unsolder the previous Rams. If it is a original
2 meg machine, I thought it was possible to upgrade by just plugging in
the right memory. Not sure if that's correct. The last 2meg one I saw did
seem to have a socket in the Ram area. Finding the right memory board may
be a problem.
If you could find a broken 4meg unit, all you have to do is just unplug
the whole board which holds TOS and the RAM and plug it back into the good
machine.
As you probably know, It is just a large single board that holds the TOS
and RAM with 2 connections that plug into the main board. Similar to a
Falcon Ram Card in a way, but on a larger scale and with the TOS of
course.
My 4meg Ram does have some wire or jumper connections."
Jo Even adds:
"... There is a door on the side of the STacy, and holes for the connector
on the MB. They must have had something in mind and dropped it for what
ever reason. Probably due to lack of power with the battery.
Thought I would explore the possibilities while I have it apart and doing
the CPU upgrade and etc. I have paper info, that shows the Bus Port
connected. The article describes it as a "special bus port" with the same
connections as the internal Mega Bus port; the pinouts are different from
the Mega plug, but electrically, it's the same.
I would think any thing that works on the Mega ST Bus would work on the
STacy if the pins are wired right. Why would they have the pins
different?"
Well folks, that's it for this time around. Let's hope that there's a
upsurge in posts for next week. Until then, keep your ears open so you'll
hear what they are saying when...
PEOPLE ARE TALKING
=~=~=~=
->In This Week's Gaming Section - Xbox Live's Games on Demand!
""""""""""""""""""""""""""""" Ready for PS4 & Xbox 720?!
Wii Sports Resort!
=~=~=~=
->A-ONE's Game Console Industry News - The Latest Gaming News!
""""""""""""""""""""""""""""""""""
Xbox Live's Games on Demand to Debut Next Month
Microsoft promised games-on-demand for the Xbox 360 at last month's E3
show, and now it's ready to launch the service on August 11.
The Xbox Live Fall Dashboard update will feature Games on Demand, a
service that (at launch) will offer more than 30 downloadable Xbox 360
games, including Assassin's Creed, BioShock, and Mass Effect. Microsoft
plans to add additional games on an ongoing basis. Pricing hasn't been
announced, so it's unclear whether the downloadable games will cost less
than the boxed versions sold at brick-and-mortar retailers.
The August update also adds goodies for Xbox live users who subscribe to
Netflix. These include improved video streaming and the ability to watched
movies and TV shows simultaneously with other Xbox Live users, Microsoft
says.
Lastly, a new Avatar Marketplace lets you outfit your digital alter ego
with branded apparel from popular fashion labels and Xbox 306 games.
Conspicuous in its absence is the previously announced support for
Facebook, Twitter, and Last.fm, which reportedly is scheduled for an Xbox
Live update sometime this fall.
Nintendo Doubles The Fun in `Wii Sports Resort'
How do you create a sequel to a product that changed the way people
think about video games?
In November 2006, "Wii Sports" - the software that's packaged with
Nintendo's Wii - introduced the U.S. audience to a new way to play. It
served as a perfect demonstration of the new console, putting the Wii's
motion-sensing controls at the service of familiar pastimes like golf
and tennis. And it was so easy to pick up and play that people who were
once intimidated by video games started Wii bowling leagues.
With more than 45 million copies in circulation, "Wii Sports" has
probably been played by more people than any game in history. A
subsequent minigame collection, "Wii Play," sold 23 million copies. So
Nintendo has high expectations for "Wii Sports Resort" ($49.99), and
there's no reason to think the company will be disappointed.
If you're a fan, you won't be disappointed either. "Resort" is bigger,
boosting the number of events from five to 12. The three sports that
have returned (golf and bowling from "Wii Sports," table tennis from
"Wii Play") are sharper, thanks to the new Wii MotionPlus accessory. And
the whole package is as lighthearted, fast-paced and accessible as the
original.
The package comes with one MotionPlus device, which attaches to one end
of the Wii remote and gives it more precise control. (It's available
separately for $24.99.) When bowling, you can flick your wrist to give
the ball some spin. Table tennis feels more like the real thing. The
updated version of golf is more demanding: You really need to focus on
keeping your swing straight or you'll be digging a lot of balls out of
the rough.
The most engrossing of the new events is archery. The Wii remote is your
bow, and you pull back your virtual arrow with the nunchuck. Nailing a
moving bull's-eye from the longest distance is a genuine accomplishment.
Frisbee may be the most challenging entry. It takes a while to master
the wrist-snap required to make accurate throws, but once you get the
knack of it, you can spend hours taking on the Frisbee golf courses.
Swordplay, basketball and "air sports" (flying and skydiving) are easier
to pick up but not quite as satisfying.
I'm less enamored with a trio of tedious water events, canoeing,
wakeboarding and "power cruising" (jet skiing). And cycling feels
nothing like the real thing, since you're using your arms to pedal.
Each sport has a decent solo mode, and achieving certain goals opens up
new game variations. But "Wii Sports Resort" is designed for more than
one player. Like the original, it's accessible to players of any age or
skill level, so anyone at your family gathering can compete. Not all the
games are keepers, but there truly is something for everybody. Three
stars out of four.
Are You Ready for The PlayStation 4 and Xbox 720?
Epic Games Vice President Mark Rein said in a recent interview that
although the video game industry has historically seen console refreshes
every four to six years, there's no need to follow that strategy this
time around. Consumers just aren't ready yet, he said.
"Over half the users who played Gears of War 2 so far do not have
HDTVs," Rein told Eurogamer in an interview. "My point is, of the systems
that are out there now, the majority of them aren't plugged into HDTVs. So
there's no way we're ready for the PlayStation 4 or the Xbox Whatever."
Rein's comments fall in line with what Sony has been touting as the
PlayStation 3's 10-year lifecycle. The hardware maker has said on numerous
occasions that the rapid console updates of the past simply don't apply in
this generation. That's why Sony, even though it's trailing far behind the
competition today, believes it can still win this console war. It believes
that its console is the only device on the market that has staying power.
For a while, many video game pundits (myself included) thought that
argument was nonsense. Surely there is something bigger and better on
the horizon, right?
Rein doesn't think so. He doesn't believe Microsoft will release a
high-powered Xbox 720 to replace the Xbox 360. On the contrary, he
thinks the future of the Xbox is based solely in Project Natal,
motion-detecting technology to control a gaming system with no controller
required.
"It's called Natal," Rein said. "That is the next Xbox."
Microsoft is saying the same thing. Just last week, the head of Microsoft
Game Studios, Phil Spencer, said that when Project Natal is made
available, it will revolutionize the market.
"When Natal comes out, it will feel like a new generation has arrived,"
Spencer said. "I see it as like the launch of the Xbox 360 back in
2005--there will be a launch portfolio of games to support it."
So perhaps Rein is right. Maybe the PlayStation 4 and the Xbox 720,
while still possible, might not make their way to store shelves for
quite some time.
It makes sense. The Xbox 360 and PlayStation 3 are network- and
HD-ready. Thanks to firmware upgrades, the hardware companies can
release incremental improvements to keep the consoles alive and well.
Since the future is both online and in HD, what makes an Xbox 720 and
PlayStation 4 so important?
Moreover, developers face some real challenges when a new console is
released. They need to learn how to exploit the hardware, which tends to
lengthen development and cost the company more cash. And even though the
Xbox 720 or PlayStation 4 might be able to provide Pixar-like graphics,
that might be far too expensive for developers, causing most companies
to balk at going that far with graphical prowess. While most gamers
might want more from their consoles, sometimes, it's just not
financially feasible.
Then there are consumers. If they've yet to capitalize on this
generation's technology, why should the industry rush to bring out new
hardware? Maybe the industry should allow consumers to catch up and
/then/ decide how to move forward.
But in the end, it's demand that will dictate the future of this space.
And that demand comes from you. So, what do you say? Are you ready for
the PlayStation 4 and the Xbox 720? Or would you rather wait until
you've fully exploited the PlayStation 3 and Xbox 360?
=~=~=~=
->A-ONE Gaming Online - Online Users Growl & Purr!
"""""""""""""""""""
The Ultimate Commodore 64 Talk @25C3
I am going to present The Ultimate Commodore 64 Talk (Everything about the
C64 in 64 Minutes) at the 25th Chaos Communication Congress 2008 (25C3) in
Berlin on 29 Dec 2008. The following article, which will be printed in the
Congress Proceedings, is supposed to give you an overview of what I am
going to talk about. If you cannot attend 25C3, you will be able to
watch a recoding afterwards, which I am going to link to. And yes, it is
a lot of information, and itll be about 256 slides (in 64 minutes) -
that is exactly the challenge. If you dont believe I cannot present all
this in a way that the audience can understand it: Watch it!
Retrocomputing is cool as never before. People play C64 games in
emulators and listen to SID music, but few people know much about the
C64 architecture and its limitations, and what programming was like back
then. This paper attempts to give a comprehensive overview of the
Commodore 64, including its internals and quirks, making the point that
classic computer systems arent all that hard to understand - and that
programmers today should be more aware of the art that programming once
used to be.
The company that became Commodore Business Machines was founded in 1954
by Jack Tramiel. The company specialized on electronic calculators, and
in 1976, Commodore bought the chip manufacturer MOS Technology and
decided to have Chuck Peddle from MOS evolve their KIM-1 computer kit (a
design that demos their new MOS 6502 8 bit CPU) into the Commodore PET
series: computers with built-in monitors for the home, school and small
business market that ended up competing with devices from Atari and Apple.
In 1981, Commodore introduced the VIC-20, a 5 KB stripped down
monitorless computer-in-the-keyboard design based on the PET for the
home computer market. This was followed by the (incompatible) higher-end
Commodore 64 in 1982 that included more PET features, came with 64 KB of
RAM (an immense amount compared to the rest of the market) and was very
aggressively priced at US$595 beating the competition by a factor of
two. This was made possible by designing and building most of the system
in-house.
Although some features of the C64 were taken from the PET models of the
time, it had to be connected to a TV set, which only made 40 columns of
text possible (as opposed to then-current 80 columns on the PET). Also,
the BASIC 4.0 codebase was stripped down to the old 2.0 feature set to
make it fit into 8 KB.
In the beginning, the C64 did well in the competition. The superior but
compatible C128 from 1985 did well, too, but was never more popular than
the C64, which continued to be sold. The direct successor to the low-end
VIC-20, the 1984 Plus/4 and its siblings, the C16 and the C116, failed,
mostly because they were incompatible with the C64, which at that time
already had a remarkable software library.
A few years after the introduction, the C64 was still offered as a
low-end alternative to the Commodore Amiga, and while it became less
popular in the USA, it gained more and more popularity in Europe. In the
early 90s, when manufacturing costs of a C64 were as low as $25, it
gained a second life in Eastern Europe. Production did not end until the
liquidation of Commodore in 1994. According to the 1993 Annual Report,
17 million C64 had been produced in by then, as well as 4.5 million C128.
A C64 only needs to be connected to power and a TV set (or monitor) to
be fully functional. When turned on, it shows a blue-on-blue theme with
a startup message and drops into a BASIC interpreter derived from
Microsoft BASIC. In order to load and save BASIC programs or use third
party software, the C64 requires mass storage - either a datasette
cassette tape drive or a disk drive like the 5.25 Commodore 1541.
Unless the user really wanted to interact with the BASIC interpreter, he
would typically only use the BASIC instructions LOAD, LIST and RUN in
order to access mass storage. LOAD8 followed by LIST shows the
directory of the disk in the drive, and LOADfilename8 followed by RUN
would load and start a program. If a tape drive is connected, LOAD and
RUN will launch the first program on tape - pressing SHIFT and the
RUN/STOP key has the same effect.
By default, typing characters without SHIFT will result in upper case
characters being shown on the screen. This can be changed by pressing
the Commodore key and SHIFT at the same time, which switches to the
upper/lower character set. This behavior is due to the fact that the
first PET only had uppercase characters, and that BASIC required
keywords unshifted - but all tutorials taught them as uppercase. This is
also the reason why in Commodores version of ASCII, called PETSCII, the
codes for uppercase and lowercase characters are reversed.
The text based user interface is not a line editor, but a screen editor,
i.e. the cursor can be moved freely on the screen, and pressing RETURN
on a line with existing text will present the text to the application as
if it were just typed in.
While a physical screen line is only 40 characters, the screen editor
logic can extend it to a logical 80 characters - whenever a character is
entered on the 40th column, the rest of the screen is moved down by one
line, opening a line that extends the previous line to 80 characters.
The C64 screen editor supports selecting one out of 16 color for the
foreground text by pressing the key combinations Ctrl+1 to Ctrl+8 and
Commodore+1 to Commodore+8. Reverse text mode can be turned on and off
with Ctrl+9 and Ctrl+0.
The C64 has a whole range of connection possibilities. On the side, it
has two 9 pin Atari-style joystick connectors that can also be used for
a mouse, light pens or paddles. On the back, there is the expansion
port, which exports the complete processor bus, allowing not only game
cartridges but also cartridges with I/O chips that map themselves into
the CPUs address space - or even cartridges that completely replace the
CPU. For a conventional TV connection, there is an RCA connector that
outputs an RF signal. For monitors, there is an extra DIN connector that
carries separate chroma, luma and audio signals (although not 100%
S-Video, it is compatible with a lot of S-Video equipment).
For connecting Commodore compatible printers and disk drives, there is a
DIN connector for the IEC bus. There is also a dedicated connector for
datasette drives. The User Port consists of several GPIO pins that can
be used for custom hardware projects, or as a RS-232 port (with TTL
levels), for which support exists in the ROM.
On the C64 motherboard, there is a dedicated IC each for the main tasks.
There is the MOS 6510 CPU, eight 64 KBit RAM chips (later consolidated
into 2), three ROM chips with KERNAL (I/O library), BASIC and the
character set (KERNAL and BASIC were later consolidated), two 6526 CIA
I/O controllers (one for keyboard and joystick, one for the IEC bus and
the user port), the 6581 SID sound chip, and the 6567/6569 VIC video
chip, as well as the RAM chip that holds the 512 bytes of Color RAM.
All non-RAM chips are custom chips designed manufactured by MOS,
Commodores inhouse chip company.
Address Space
The 8 bit C64 design has a 16 bit address bus, allowing the CPU to
address 64 KB of memory. Since the C64 has 64 KB of RAM, filling the
complete address space, ROM and I/O chips are mapped into regions of the
address space that are shared with RAM: The CPU can switch these regions
between RAM and a second or third mapping. These regions are as follows:
* $0000-$9FFF: RAM
* $A000-$BFFF: RAM or BASIC ROM
* $C000-$CFFF: RAM
* $D000-$DFFF: RAM or memory mapped I/O chips or character ROM
* $E000-$FFFF: RAM or KERNAL ROM
In contrast to CPUs like the Z80 and the 8086, and like most modern
CPUs, I/O devices are memory mapped on the C64s 6510 CPU. The mapping
is as follows:
* $D000-$D3FF: VIC video controller
* $D400-$D7FF: SID sound controller
* $D800-$DBFF: Color RAM
* $DC00-$DCFF: CIA 1 I/O controller
* $DD00-$DDFF: CIA 2 I/O controller
* $DE00-$DFFF: for extensions on the expansion port
6502 CPU
The CPU inside the C64 is a 0.985 MHz (on PAL) MOS 6510, which is a
close derivative of the well-known 8 bit little-endian MOS 6502. The
6502 was introduced in 1975 by MOS Technology, a company formed earlier
the same year by former Motorola engineers, with engineering headed by
Chuck Peddle. The philosophy of the 6502 was to have a reduced
instruction set and a small register file, making it simpler and faster
than CPUs like the Z80 at the same clock speed, as well as cheaper to
manufacture.
Unlike most modern CPUs, the 6502 does not have a set of general purpose
registers. Instead, it has a single accumulator A (for arithmetic and
logic), two index registers X and Y (for incrementing, decrementing and
indexing memory) and a stack pointer. All these registers are 8 bits.
The processor status, consisting of the negative (N), overflow (V),
break (B), decimal (D), interrupt (I), zero (Z) and carry (C) flags is
exposed as register P. The program counter (PC) is 16 bits wide. The
fact that the stack pointer is 8 bit means that the stack is confined to
the area between $0100 and $01FF in the address space, i.e. the upper
half of the effective stack pointer is hard-coded to $01. There is
another special area in the address space: The first 256 bytes, at $0000
to $00FF are referred to as the zero page (ZP). Many instructions
support special encodings for zero page addresses, which saves one byte
in the instruction encoding as well as at least one cycle of execution
time. This can be seen as an extension of the register file to another
256 (though external) registers.
All opcodes are one byte, and have 0, 1 or 2 byte operands. The 8×8
opcode matrix is somewhat logical (e.g. branch instructions are encoded
as $10, $30, $50), but there is no easy rule to construct the opcode
table. Nevertheless, the opcode table is a minimal encoding for optimal
decoding in the 6502s internal PLA ROM.
Instruction Set
The instruction set is very streamlined, and avoids redundancies. There
are load instructions (LDA/LDX/LDY to load A, X and Y respecively),
store instructions (STA/STX/STY), read-modify-write instructions (logic:
ASL/LSR/ROL/ROR, count: INC/DEC), arithmetic (ADC/SBC; note that these
always include the carry: CLC/ADC is a regular addition, and SEC/SBC is
a regular subtraction, because of the ones complement logic), compare
(CMP/CPX/CPY; these are subtractions without storing the result), logic
(AND/ORA/EOR, and BIT, which is AND without storing the result), as well
as branch instructions, flag manipulation, register transfer and stack
manipulation.
Addressing Modes
Each instruction supports one or more addressing modes. Common
instructions like LDA (load accumulator) support more addressing modes
than less common ones (BIT).
* The immediate addressing mode is indicated with a # sign: LDA #$17
loads the immediate value of $17 into the accumulator.
* Absolute addressing specifies a 16 bit address as an operand: LDA
$0314 loads from the memory address $0314.
* Zero page addressing is an optimized version of absolute
addressing: LDA $02 will read from address $0002 in memory, but
the instruction can be encoded more tightly, and execution is faster.
* Absolute-X-indexed addressing reads from a specified address, to
which the contents of the X register is added. LDA $0200,X reads
from the address $020A, in case X is $0A. This allows reading from
tables.
* Absolute-Y-indexed is the same thing, but with the Y register.
* Zero-Page-X-indexed is an optimized version of Absolute-X-indexed.
LDA $F0,X reads from the Xth location in a table stored starting
at $00F0 in memory. Note that all zero page addresses will wrap
around, so $F0 + $10 = $00.
* Zero-Page-Y-indexed is the same thing, but with the Y register.
* Zero-Page-X-indexed-indirect adds X to a specified zero page
address, reads a 16 bit pointer from the resulting address and
finally accesses memory at that address. So LDA ($80,X) will read
from an address specified by the array of pointers at $0080 and
the index X into the array. This addressing mode is rarely used.
* Zero-Page-indirect-Y-indexed treats two consecutive bytes in zero
page as an address and adds Y to the address. LDA ($14),Y will
read from $E020, if the address stored at $14/$15 is $E000 and Y
is $20. This addressing mode is the most convenient way to work
with pointers, as no register can hold 16 bits.
Register Transfer and Stack
There are several 1 byte instructions without operands that move data
between registers. TAX, TXA, TAY and TYA move between A, X and Y. TSX
and TXS copies between X and the stack pointer.
The stack pointer always points to the next address that is written to.
This means that an empty stack has a stack pointer of $FF, and pushing a
value first writes the value and then decrements the stack pointer. The
6502 can move the accumulator from and to the stack (PHA/PLA), as well
as the processor status P (PHP/PLP).
Control Transfer
Next to the absolute JMP instruction, there is an indirect version that
jumps over a vector (e.g. JMP ($FFFC)). JSR (jump to subroutine) only
has an absolute version, and stores the address of the next instruction
minus one on the stack. RTS (return from subroutine) takes the address
from the stack, adds one, and moves it into the program counter. The
'minus one' logic was chosen because it could save one cycle in the
implementation of JSR.
A hardware interrupt, unless disabled by a set interrupt (I) flag,
pushes the address of the next instruction minus one (just like JSR),
pushes the processor status afterwards, disables interrupts, and jumps
over the vector at $FFFE/$FFFF. RTI return from interrupt) is the same
as the combination of PLP and RTS. BRK causes a software interrupt and
behaves the same as a hardware interrupt, except that it sets the B flag
in the processor status on the stack to 1 (a hardware interrupt sets it
to 0). Note that the B flag does not exist in the actual processor
status register, the corresponding bit is only used in a status byte on
the stack.
From a software perspective, NMIs behave the same as IRQs, but they
cannot be masked, and they use the $FFFA/$FFFB vector. The reset vector
is at $FFFC/$FFFD.
Flags and Branches
All load and logic instructions set N and Z accordingly, shift
instructions also modify C, and arithmetic instructions touch N V, Z and
C. The D (decimal), I (interrupt disable) and C flags can be set and
cleared programmatically (CLD/SED, CLI/SEI, CLC/SEC), while the V flag
can only be cleared (CLV). Conditional branches are possible based on
the value of the negative (BPL/BMI), overflow (BVC/BVS), zero (BNE/BEQ)
and carry (BCC/BCS) flags. Branches encode an 8 bit relative offset and
can therefore reach code in the area of +127 and -128, counting from the
byte after the branch instruction. Since a compare is the same as a
subtraction, BCC is a branch on (unsigned) below, and BCS is a branch on
above-or-equal.
NOP
NOP (no operation) does nothing. Its encoding is $EA.
Decimal Mode
If the D flag is set, all ADC and SBC operations will be BCD-adjusted
afterwards, i.e. $09+$02 wont be $0B, but $11, since 9+2=11. The BCD
correction circuit has been patented in US patent 3,991,307.
Cycle Counting
It is quite straightforward to find out how many cycles an instruction
takes. As a rule of thumb, an instruction takes as many cycles as the
number of memory fetches it has to perform, but at least two.
Therefore, single-byte opcodes (one byte fetches; NOP/TAX/INX etc.) as
well as instructions with immediate operands take two cycles. Zero page
instructions take three memory accesses (opcode, address, data), so they
are three cycles. Absolute instructions take four accesses (opcode,
address low, address high, data), so they are four cycles.
Read-modify-write instructions (INC/DEC/shift/rotate) are an exception:
They require 4 memory accesses for the zero page case and 5 otherwise,
but they take 5 and 6 cycles, respectively.
Branches take 3 cycles if they are taken and two if they are not taken.
And extra cycle has to be added if the branch crosses a page boundary.
JMP is 3, push is 3, pull is 4, JSR and RTS are 6 each.
All other timings can be looked up in the 6502s reference, but they are
very easy to memorize.
Common Tricks
The BIT instruction exists in a two-byte (immediate operand) and
three-byte (absolute operand) variant. Since BIT only changes the flags,
it effectively skips one or two bytes in the instruction stream. This
can be used to replace a two-byte branch or a three-byte JMP with a
one-byte BIT if only one or two bytes have to be skipped.
The architecture allows safe self-modifying code, so a common
optimization for copy loops is to use LDA $nn00,X and STA $mm00,X,
looping X from $00 to $FF and then incrementing the bytes that encode nn
and mm for the next page. Compared to a LDA (zp1),Y: STA (zp2),Y
sequence, this gets the inner loop down from 16 cycles (5 LDA, 6 STA, 2
INY, 3 BNE) to 14 (4 LDA, 5 STA, 2 INY, 3 BNE).
A PHA/PLA combination is 7 cycles, while an STA/LDA combination in the
zero page is 6 cycles, so unless there is no free zero page space,
PHA/PLA should be avoided to quickly store a value. Using an absolute
store to write the value into the operand of a future immediate load
(i.e. self modification) is the same speed at the zero page solution,
but does not waste zero page space.
An elegant way to store a flag is to have it in bit #7 of a zero page
address. While a load/store combination has to be used to set the flag
(or the slower, but register-preserving SEC/ROR combination), it can be
cleared with a simple LSR (5 cycles) and tested with BIT (3 cycles),
without affecting register contents.
Since the 6502 is so register starved, only 3 bytes can be passed to a
subroutine in registers. Also, the stack is small, and accessing it is
slow, so stack frames as seen on modern architectures are very uncommon.
Many applications and libraries (e.g. GEOS) use a dedicated area in the
zero page as virtual registers.
The 6502 has no instructions for multiplication, division or floating
point arithmetic. Most 6502-based computers have a BASIC interpreter in
ROM though, and they typically include a math and floating point library.
Bugs and Quirks
The original 6502 implementation has a series of bugs and other
anomalies that have never been fixed in MOS chips (not counting the
65CE02, which was only used in Amiga peripherals).
The indirect version of JMP loads the program counter from the wrong
address, if the vectors address lies on a page boundary: JMP ($23FF)
will read the address from $23FF and $2300 instead of $23FF and $2400.
When in decimal mode, the negative flag reflects the original binary
result, not the effective decimal result.
If a software interrupt (BRK) and a hardware interrupt occur at the same
time, the BRK is dropped.
STA with the absolute-indexed addressing mode takes first reads from the
absolute address without the index register added, and then reads again
from the correct address. LDX #$07 STA $DC0D,X will first read from
$DC0D, discard the result, and then write to $DC14. On the C64, this
read form $DC0D would ACK all pending CIA 1 interrupts, while it is only
supposed to write to $DC14.
Read-modify-write instructions with absolute addresses first read the
value, but one cycle before they store the result, they store the
original value again. On a C64, this can be seen when incrementing the
screen border color at a defined area of the screen, as every write to
the register will cause a tiny gray dot on the screen (on later HMOS
versions of the VIC). When this is used with certain I/O ports, this can
have other side effects. The latter two quirks have been used heavily
for obfuscating copy protection software.
Instruction decoding in the 6502 is done by a PLA that compares the
current cycle number within the instruction and the current opcode
against a ROM of 130 mask lines, of which any number can fire
independently. The outputs of these lines are then fed into components
like the ALU, bus control, register control and program counter logic.
The instruction set only consists of 151 defined opcodes, and since
handling the remaining 105 opcodes as NOPs or traps would have required
extra lines in the PLA, they will match against some lines that were
meant for instructions with similar opcodes. Some of these 'illegal
opcodes' lead to useful results and are used in some software (SAX =
store A & X), but most of the instructions make little sense (LAS =
loads from memory, ANDs it with S and stores it into A, X and S), and
some even lock up the CPU, disabling IRQs and NMIs (CRA/KIL).
The MOS 6510
Except for the pin layout, the MOS 6510 that is used in the C64 differs
from the generic MOS 6502 in two ways: It can make the bus tri-state
when not used, so the VIC can use it, and it has a 6 bit I/O port built
in, which can be controlled using zero page locations 0 and 1. In
register 0, each bit from 0-5 set it to output if 1, and to input if 0.
Bits 0-5 in register 1 are the actual I/O pins. On the C64, bits 0-2 are
outputs and control bank switching, they turn the ROMs and the I/O area
on and off. Bits 3-5 go to the tape connector and control the motor and
the data sent to the head, and detect whether a key on the tape deck is
pressed.
BASIC
Microsoft had a strong position in the market for (mostly ROM) BASIC
interpreters in 8080-based home computers when the MOS 6502 was released
in 1975, so they rewrote their interpreter in 6502 assembly. Microsoft
BASIC was pure 6502 code with a minimal character I/O interface to the
machines 'monitor', i.e. I/O library.
Commodore decided to license the interpreter for the 1977 PET and
extended it slightly to interface with their disk and tape libraries.
Commodore BASIC was very buggy, so they went back to Microsoft for an
update, which, with the Commodore changes re-applied, shipped in newer
PETs as BASIC V2. For version 4, Commodore added several instructions
for more conveniently dealing with disk.
Being a low-end machine, Commodore took the bugfixed BASIC V4 codebase
and removed all features after V2, making it independent of the
machines graphics and sound features again, and fitting it back into 8
KB, and shipped this version on the VIC-20. The Commodore 64 got the
almost exact same version, but it runs at a different memory address
($A000-$BFFF).
Microsoft BASIC is a line-based editor, that is, lines can be shown with
the LIST command, and they can be modified by re-typing them. This
integrates nicely with the KERNAL screen editor: The cursor can be moved
up to LISTed lines, the lines can be modified, and when RETURN is
pressed, the whole line is fed into BASIC again.
A nice feature of this and later versions of Commodore BASIC is the fact
that all important parts, like the tokenizer, the detokenizer and the
interpreter loop jump over a jump table in RAM before they do their
work, allowing the user to extend BASIC arbitrarily. The most well-known
BASIC extension is Simons BASIC, a cartridge that maps 8 KB of extra
ROM at $8000-$9FFF.
KERNAL
The C64 has an 8 KB I/O library at $E000-$FFFF which is utilized by
BASIC, but is intended to be used by other applications as well. All
Commodore 8 bit systems have a standardized library call interface in
the form of jump tables at the very top of memory that call into
machine-specific functions for I/O.
KERNAL is started form the RESET vector, initializes the machine, sets
up an interrupt service routine that handles the keyboard, animates the
cursor and does the real time clock. The C64 has a hardware clock in
each of the CIA chips, but KERNAL has not been updated to use this
feature since the VIC-20.
KERNAL provides an abstract character I/O interface to a number of
devices. All devices support open, read, write and close. The open call
takes three parameters: The logical file number (there is a maximum of
16 channels), the device number and the secondary address. There are 32
device numbers statically assigned to the devices. The 8 bit secondary
address can signal something to the device, like speed or an operation
mode. Some devices (tape and IEC) support an optional filename.
Device 0 is the keyboard. While KERNAL exports raw key presses, the
keyboard can also be accessed through character I/O, which will go
through the screen editor and replay all characters on the screen that
are in the line of the cursor, regardless of whether the user typed them
or they had been there before.
Device 1 is the tape drive. KERNAL reads and writes blocks of data at a
time and buffers them for character I/O.
Device 2 is RS-232. KERNAL contains a very sophisticated (but rarely
used) software RS-232 implementation that supports up to 2400 baud.
Device 3 is the screen. KERNAL interprets special codes, manages the
cursor position and handles scrolling.
Devices 4 and greater will be directed to the IEC bus. By convention,
devices 4 to 7 are printers and plotters, and devices 8 to 30 are floppy
drives or hard disks.
KERNAL allows interacting with the IEC bus manually by sending TALK and
LISTEN requests to the bus.
GEOS
While KERNAL is a minimal character-based operating system in ROM, there
is also a disk-based operating system with a graphical user interface
for the C64. GEOS was released by Berkeley Softworks in 1986 and
Commodore bundled it with the C64 for some time. The GUI, which can be
controlled by a joystick or a mouse, runs in 320×200 graphics mode and
resembles early versions of MacOS. GEOS is a 16 KB library that includes
an optimized disk interface (faster, support for timstamps, icons and
multi-fork 'VLIR' files), library code for drawing to the screen, high
level UI primitives for menus, buttons and dialog boxes (with callbacks)
and a simple memory swapping facility. Furthermore GEOS allows input and
printer driver plugins, as well as proportional fonts in different
sizes. Internally, GEOS has a jump table to its library routines that
consists of about 150 entries.
GEOS came with applications like GeoPaint and GeoWrite; Berkeley
Softworks themselves offered solutions like GeoPublish and GeoCalc, and
more software was available from third parties.
GEOS only requirement is a 1541 disk drive, but a 3.5" 1581 drive, a
RAM extension or one of the later hard drives helped speed it up a lot.
6526 CIA
The C64 has two identical 6526 CIAs (Complex Interface Adapter) that are
mostly used for I/O. One CIA features 16 general purpose I/O pins (8 bit
port A and 8 bit port B) that can be used either as an input or an
output, two programmable timers and a real-time-clock.
The timers have 16 bit counters and count down by one either on each
clock cycle, or on an external event, or on a timer A underflow (in the
case of timer B). This allows concatenating the timers to one 32 bit
timer. On an underflow, the CIA can be programmed to cause an IRQ or to
send data through a serial shift register. The CIA also supports
receiving data through a shift register.
The real-time-clock has a resolution of 1/10 of seconds and supports
generating interrupts at a certain time.
CIA 1 is hooked up to the keyboard and the joystick ports. Since the
keyboard consists of 64 keys (plus SHIFT LOCK, which is parallel to the
left SHIFT key, and RESTORE, which is directly connected to the CPUs
NMI line), these can be laid out in a 8×8 matrix of lines, key presses
connecting the intersections. One side of the matrix is connected to
port A (output), and the perpendicular side is connected to port B
(input). The keyboard driver can now write the values of $01, $02, $04
etc. in port A and test the input of port B to see which keys are
pressed. The two joysticks are connected in parallel to port A and port
B, so they can cause spurious keyboard events.
CIA 2 is hooked up to the IEC bus, and I/O lines control the VIC bank.
The rest is exposed on the user port, and can be used for RS-232.
KERNAL uses CIA 1 for the 60 Hz system timer, but, apart from the ports,
doesnt use any of the extra features of either CIA.
6581 SID
The SID (Sound Interface Device) is a whole topic of its own.
6567/6569 VIC
The video chip inside the C64 is called the MOS 6567/6569 VIC-II (Video
Interface Controller) - the video chip in the VIC-20 had been the
original VIC, and was the reason for the marketing name of the VIC-20.
The VIC supports a 40×25 text mode, a 320×200 bitmap mode, 16 colors and
8 sprites - all of these features have lots of sub-modes and options.
The amount of memory the VIC can address is 16 KB, and while by default,
it accesses the first 16 KB of the C64 RAM, it can be configured to use
any of the four banks.
The 16 colors of the VIC are divided into two sets of eight. The first
eight are the more important colors, as some modes only support the
first eight. The colors are, in the original order: black, white, red,
cyan, purple, green, blue, yellow, orange, brown, pink, dark gray, gray,
light green, light blue and light gray.
Character Mode
The C64 has two built-in character sets that the VIC can access. They
can be shown on the screen by writing the numbers 0 to 255 into screen
RAM (at $0400 by default). The default font has uppercase characters and
lots of line-drawing symbols in the lower 128 characters, and the second
half consists of the same characters, but inverse. The alternative font
has upper- and lowercase characters and omits some of the symbols.
The foreground color of the characters can be changed by writing the
color numbers into the Color RAM, which is located at $D800-$DBFF. There
is one byte per character, but only the lower 4 bits are actually
preserved by Color RAM.
Each character is 8×8 pixels, and stored as eight bytes in the character
ROM (or RAM, if a user-defined character set is enabled), one line being
one byte. A 1-bit will take the color from the Color RAM ($D800-$DBFF),
and a 0 bit will take it from the global background color register
($D021). The pixel matrix is determined by looking up the character
index in the screen RAM (at $0400-$07FF by default) and consequently
looking up the pattern the current character set (the VIC sees the
default font at $1000, although for the 6502 it is invisible there).
In Extended Color Mode (ECM), it is possible to chose between one of
four background colors (registers $D021 to $D024) with the upper two
bits of the character index, but then only 6 bits will be used to look
up the character pattern, decreasing the number of possible characters
to 64. The built-in (uppercase) character set is well-suited for this:
While it is similar to the ASCII encoding, it has the uppercase
characters mapped to codes $01 to $1A, so the most important characters
are within the first $40.
Multi-Color Character Mode allows up to four colors per character and is
intended for tile-based games, like platformers. If bit 3 of the value
in Color RAM is 0, then the character gets displayed just like in
non-multicolor mode, but colors are restricted to the first eight. If
bit 3 is 1, then pairs of horizontally adjacent bits are combined in
their meaning: 00 represents the screen background ($D021), 01 is the
second background register ($D022), 10 is the third background register
($D023), and 11 is the color specified in bits 0-2 of the Color RAM.
Pixels in these characters are twice as wide, so the resolution of a
character is 4×8.
Bitmap Mode
In hi-res graphics mode, the VIC supports a resolution of 320×200, which
uses the same pixel frequency as 40×25 character mode (40*8=320,
25*8=200). The bitmap can reside at $0000 or $2000, and the VIC reads
one byte for 8 pixels. But hi-res mode does not only support monochrome
graphics: The foreground and background colors of each 8×8 tile are
taken from the high and low nibble of screen RAM, which would otherwise
be unused. Color RAM is not used in this mode.
The encoding of the bitmap is identical to the encoding of a character
set, making it a non-linear framebuffer: The first eight bytes of the
bitmap represent the pixels in the tile at character position (0,0), the
second eight bytes represent the tile at character position (1,0), which
is pixel position (8,0), and so on. This layout makes pixel addressing
in software slower.
In Multi-Color Bitmap Mode, the horizontal resolution is halved to
160×200, and pixels are twice the width. Every set of two bits in the
encodes one of four colors per tile: 00 takes it from the global
background register ($D021), 01 and 10 take it from the upper and lower
nibble of screen RAM, respectively, and 11 takes it from Color RAM.
Scrolling
The VIC supports hardware X and Y scrolling by 0 to 7 pixels. Since the
40th column is half visible and another column left of the first column
is half-visible when the horizontal shift register is set to e.g. 4, a
41th column would be needed. Instead, it is possible to switch the
screen to 38 column mode, i.e. the whole screen is a little narrower,
and more border is shown on the left and on the right. The screen can
also be switched from 25 to 24 lines the same way.
Sprites
The VIC has eight hardware sprites (also called MOBs, movable objects).
Each sprite is 24×21 pixels, which is encoded in 63 bytes. Set bits will
be drawn in the sprites individual foreground color, and cleared bits
will be transparent. The index to the sprites bitmap data in memory is
an 8 bit value that is read from the last 8 bytes of screen RAM - since
the screen is only 1000 characters, the last 24 characters of the
$0400=1024 bytes area would otherwise be unused.
There is also a multicolor mode for sprites, which makes pixels twice as
wide and decreases the horizontal resolution to 12 pixels. In this mode,
00 is still transparent, and 10 encodes the sprites individual color.
The codes 01 and 11 take the color out of the sprite multicolor
registers ($D025 and $D026), which are shared among all sprites.
Sprites can be positioned at arbitrary pixel positions on the screen,
and overlap. In this case, sprites with lower numbers have priority over
sprites with higher numbers. Each sprite can either be shown in front or
behind background pixels. Sprites can be X- and Y-expanded by a factor
of two, and collision of two sprites or of a sprite and background
pixels is detected by hardware: Whenever two non-transparent sprite
pixels are drawn at the same position on the screen, they have collided.
Whenever a non-background pixel is drawn by the character generator at
the same position where a non-background pixel of a sprite is draw, the
sprite has collided with the background. An exception from this rule is
the 01 code in the character data, which also counts as background. This
way, a background picture can be constructed that does not cause
collisions in certain areas. In practice, most newer games do not use
the hardware functionality, but instead test for overlapping sprite
bounding boxes in software.
Memory Layout
The VIC can address 16 KB at a time. All VIC data structures can be
stored anywhere in these 16 KB, but they have to be aligned to their size.
* The screen RAM is $0400 bytes in size and can be at $0000, $0400,
* The character set is $0800 bytes, and can be at $0000, $0800,
* The bitmap is $2000 bytes and can be at $0000 or $2000.
* Sprites are $40 bytes, and can be at $0000, $0040,
Two GPIO pins of the second 6526 CIA are connected to bits 6 and 7 of
RAM when the VIC accesses it. By changing the lower 2 bits of $DD02, the
VIC can be switched between banks $0000-$3FFF (11), $4000-$7FFF (10),
$8000-$BFFF (01) and $C000-$FFFF (00).
If the VIC is set to banks $0000 or $8000, then the two built-in
character sets shadow RAM in the area of $1000-$1FFF. This means that
the built-in character set can be used on those banks without occupying
RAM, but it also means that the area from $1000-$1FFF cannot be used for
bitmap, screen RAM or sprite data either.
For timing reasons, color information is not taken from main RAM, but
from a dedicated Color RAM. These $0400 half-bytes are accessible to the
C64 at $D800-$DBFF and can not be bank switched.
Timing
For advanced VIC programming, it is necessary to not just set up a
certain mode and have the VIC display it, but to reprogram the VIC while
it is drawing the picture. For this, it is necessary, to understand its
timing.
While the pixels within the screen area are 320 by 200, the VIC actively
draws pixels in the border color outside of this area, which (on PAL) is
403×284 pixels. Analog TV standards specify an H blank area at the end
of every line, and V blank area at the end of every screen. So counting
this timing as pixels, this gives an absolute resolution of 504×312
pixels. The interesting and very useful connection about the pixel clock
and the system clocks is that an 8 pixel character is drawn every system
clock cycle, i.e. about 1 million times a second. The 504 horizontal
pixels therefore mean that a line is drawn on the screen every 63
cycles. With this information, it is possible to do cycle-exact timing
of assembly code to switch a VIC register at an 8 pixel granularity.
Further timing details (badlines, sprite timing), as well as the
application of this information to do tricks like FLD, FLI and AGSP
would go beyond the scope of this article, but are talked about in the
presentation at the 25th Chaos Communication Congress.
Memory Configuration
In a running system with BASIC and KERNAL, the BASIC and KERNAL ROMs are
turned on and visible at $A000-$BFFF and $E000-$FFFF respectively, and
at $D000-$DFFF, the I/O area is visible. Using the 3 lowest bits in the
processor port at address 1, this configuration can be altered. The ROMs
can be turned off, revealing RAM instead, and the I/O area can be
configured to show either RAM or the character set ROM. Note that
writing to ROM will always direct the data to the underlying RAM.
In practice, many programs run in the default configuration and use both
KERNAL library routines, as well as functions in BASIC, to keep their
own code as small as possible. More recent programs and almost all games
turn off all of ROM, to get direct control of the interrupt vector
without having to go though the KERNAL handler first. The I/O area is
typically configured to show the I/O registers and Color RAM, and only
rarely switched to a different configuration to temporarily access the
RAM underneath. A few applications read the character ROM at program
start and modify the copy.
The C64 supports another ROM bank at $8000-$9FFF, which can only be
serviced by an external cartridge connected to the expansion port. Also,
the $A000-$BFFF bank can be overridden by an external ROM. If KERNAL
detects the magic string 'CBM80' at $8004 on startup, it will jump to
the code of the cartridge right away.
Expansion port cartidges can also put the C64 into 'ULTIMAX' mode, in
which the it can play game cartridges for the failed C64-based stripped
down 'ULTIMAX' system ('Commodore MAX', 'VC-10'): All internal ROM is
disabled, $8000-$9FFF and $E000-$FFFF show external ROM, RAM is only
visible at $0000-$0FFF, and the VIC has a different view on the address
space. This mode is used by freezer cartridges which can use it to
replace the $E000-$FFFF bank and thus override the hardware vectors.
Tape Interface
The tape interface consists of a single line each for data input and
output, motor control and key sense. The raw data is read from and
written to the data lines, and all encoding and decoding of the data
stream is done in software. 3 of the required lines are connected to the
processor port at zero page location 1, and one (data input) is
connected to CIA 2.
IEC Bus
The IEC bus is a serial version of the IEEE-488 bus used on the PET.
Devices on the IEC bus are daisy-chained, and are all connected to the
same three lines: ATN (attention), clock and data. IEC has a single bus
master, which is the computer. It is the only device to ever raise ATN,
while every device can output to clock and data, depending on the state
of the bus.
If the computer raises ATN, every device on the bus listens for the
command which includes the 5 bit device number (0-30) and compares it
with its own. The protocol on who sends and who receives is determined
by the computer sending TALK/UNTALK and LISTEN/UNLISTEN commands.
While KERNAL exports the interface at this level, it also allows
high-level open, close, read and write operations on the IEC bus, as
well as load and save operations. The BASIC LOAD and SAVE commands are
directly hooked up to this interface.
The IEC bus was designed for the serial shift register in the VIA
(Versatile Interface Adapter) of the VIC-20 and its disk drive, but it
turned out that the VIA had a bug that made the shift register unusable,
so the IEC protocol had to be implemented in software. While the C64 has
CIAs, in which the bug has been fixed, the 1541 still used VIAs. It
wasnt until the C128 (in its native mode only) that the computer could
talk to the floppy drive (Commodore 1570/1571/1581) in its intended speed.
1541 Disk Drive
The Commodore 1541 Disk Drive is the most common disk drive used with
the C64. It uses 5.25" SS/DD (single side, double density) disks, but
disks can be flipped, and the other side can be used as well, if the
disks are double sided. The 1541 does not use the index hole, and uses
software markers (SYNC) instead to be able to tell the start of a
sector. Due to reliability problems of early drives, the 1541 only uses
35 out of the 40 possible tracks on a 5.25" disk. The tracks have a
variable number of 256 byte sectors, ranging from 21 on the outside to
17 on the inside. The data is written in 4 different speeds. This makes
an overall 683 sectors, or 174,848 bytes.
The file system is stored on track 18. Track 18, sector 0 contains the
disk name and the BAM (block availability map), which stores one bit per
sector (1 = free). Track 18, sector 1 is the first sector containing
directory entries: There are eight 32 byte entries per sector, with a
maximum filename length of 16 characters. The first two bytes of a
directory sector point to the next directory entry sector.
The files on disk are also stored as a linked list. The first two bytes
of every sector are either the track and sector number of the next
block, or the first byte is 0 and the second byte is the number of valid
bytes in this sector.
The 1541 is a stripped down version of the PET drive series, which had a
parallel connection, and contained two 6502 CPUs: One for doing the
filesystem and communicating with the computer, and one for reading data
from disk and writing data to it, as well as encoding and decoding the
data. The 1541 only has a single 6502 CPU running at 1 MHz, which (using
timer IRQs) regularly switches itself between the two modes. The two
virtual CPUs still communicate with each other using a messaging
interface in the zero page. The 1541 has 2 KB of RAM at $0000-$07FF.
The 1541 has two VIA I/O controllers at $1800 (for the IEC bus) and at
$1C00 (for the drive). The firmware is located at $C000-$FFFF.
Since loading an application or a game takes minutes on an unmodified
C64, several 'floppy speeders' appeared (either as software on disk or
built into applications, as ROM extension cartridges, or as internal
replacement ROMs), that
consisted of implementations of more optimized
protocols for the IEC bus for both the C64 and the 1541. The 1541 code
was uploaded using the old bus protocol. Such a new protocol would for
example not do a handshake on every bit using the clock line, but shift
a complete byte through in 4 steps, two bits at a time, using the clock
and data line at the same time. This would of course only work if both
CPUs were not interrupted. VIC timing on the C64 side could already
affect this, so many floppy speeders turned off the screen while loading.
Other Peripherals
The 1541 is the necessary companion to a C64. It can be replaced by a
1570 (1541 with fast bus routines for the C128) or a 1571 (double-sided
1570), since they include a 1541 compatibility mode. The 3.5" Commodore
1581, which supports 880 KB per disk, can hardly be a replacement for a
1541, because most applications contain their own floppy speeders that
make lots of assumptions on the exact on-disk format. For GEOS, it can
be very useful though.
Creative Micro Devices sold and continues to sell a line of hard drives
that have an IEC connection but contain a 3.5" SCSI drive inside.
Although they have a 6502 CPU built in and allow code execution on their
CPU, they are not compatible enough to replace a 1541 either.
Several memory extension cartridges exist for the expansion port of the
C64: The Commodore REU (contains a DMA chip that transfers data between
itself and main RAM), as well as the third party GeoRAM (maps a block to
the $DE00-$DFFF area) and RAMLink (battery backed, designed as RAM disk).
Freezer cartridges like the Action Replay and the Final Cartridge were
not only popular because they could dump all of memory to disk and thus
copy certain copy-protected games, but also because they featured floppy
speeders that disabled the original routines directly at startup time,
without any effort from the user.
In the mid 90s, CPU speeders for the expansion port became popular. The
8 MHz Flash 8 is rare today, but many enthusiasts have a SuperCPU, which
replaces the onboard CPU with a 20 MHz 65C816, which has a native 16 bit
mode that can address up to 16 MB or RAM. There are a few applications
and games that require a SuperCPU. The speedup of GEOS with a SuperCPU
is significant.
In the 2000s, the enthusiast scene created all kinds of peripherals,
like ethernet interfaces, IDE interfaces and SD card readers.
And there are not only peripherals: In 2004, the Commodore 64 DTV, a
reimplemented C64 appeared in the form of a Joystick. The device is
fairly compatible and can be extended to connect to a keyboard and a 1541.
This entry was posted on Monday, December 15th, 2008 by Michael Steil at
14:15 and is filed under archeology <http://www.pagetable.com/?cat=8>.
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<http://www.pagetable.com/?feed=rss2&p=53> feed. You can leave a
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A-ONE's Headline News
The Latest in Computer Technology News
Compiled by: Dana P. Jacobson
Shortage of Cyber Experts May Hinder Government
Federal agencies are facing a severe shortage of computer specialists,
even as a growing wave of coordinated cyberattacks against the
government poses potential national security risks, a private study found.
The study describes a fragmented federal cyber force, where no one is in
charge of overall planning and government agencies are "on their own and
sometimes working at cross purposes or in competition with one another."
The report, scheduled to be released Wednesday, arrives in the wake of a
series of cyberattacks this month that shut down some U.S. and South
Korean government and financial Web sites.
The recruiting and retention of cyber workers is hampered by a
cumbersome hiring process, the failure to devise government-wide
certification standards, insufficient training and salaries, and a lack
of an overall strategy for recruiting and retaining cyber workers, the
study said.
"You can't win the cyber war if you don't win the war for talent," said
Max Stier, president of the Partnership for Public Service, a
Washington-based advocacy group that works to improve government
service. "If we don't have a federal work force capable of meeting the
cyber challenge, all of the cyber czars and organizational efforts will
be for naught."
The study was drafted by the partnership and Booz Allen Hamilton as the
Obama administration struggles to put together a more cohesive strategy
to protect U.S. government and civilian computer networks.
The size of the government's cyber work force is largely unknown,
because agencies often classify their employees differently. The
Pentagon says it has more than 90,000 personnel involved with
cybersecurity, while the non-defense department civilian cybersecurity
work force has been estimated at 35,000 to 45,000. Intelligence
community estimates are classified.
While President Barack Obama has declared cybersecurity a top priority,
the White House so far has been unable to fill its new cyber coordinator
position - a job regarded as critical.
The study recommends that the yet-unnamed federal cyber coordinator lay
out a strategy to meet the government's work force needs, set job
classifications, enhance training and lead a nationwide effort to
promote technology skills, including through the use of scholarships.
The federal government's vulnerabilities have been underscored by
cyberattacks that breached a high-tech fighter jet program and the
electrical grid, although no classified material was compromised.
Earlier this month, unknown hackers knocked several U.S and South Korean
government Web sites off line in a widespread and unusually resilient
computer attack.
Ron Sanders, chief human capital officer for the national intelligence
director's office, said it is difficult to draw a link between the work
force shortages and the increased cyber threats against the government.
"It's hard to say that there is any cause and effect there," said
Sanders, adding that the U.S. probably will have to live with the nearly
constant attacks. But, he said, the intrusions have heightened awareness
of the problem, forcing officials to focus on the hiring needs.
Microsoft Trying To Settle Browser Case
Microsoft Corp. will offer computer users a choice of Web browsers to
ward off new European Union antitrust fines, EU regulators said Friday.
The European Commission has charged the company with monopoly abuse for
tying the Internet Explorer browser to the Windows operating system
installed on most of the world's desktop computers.
It said Microsoft is suggesting that consumers pick a browser from
several offered on a ballot screen in its new software release, Windows
7, which will go on sale Oct. 22.
Windows would still include Internet Explorer, but users would be able
to disable it. Computer manufacturers could also choose to install other
browsers, set them as default and disable Internet Explorer.
Regulators did not say if this was enough to settle antitrust action and
allow the company to avoid new fines on top of the euro1.7 million that
Microsoft already has paid in a series of battles with the EU executive.
"The Commission welcomes this proposal and will now investigate its
practical effectiveness in terms of ensuring genuine consumer choice,"
they said.
EU officials have warned that their case targets a possible violation of
antitrust rules since 1996. Microsoft's proposal affects only its latest
browser.
Microsoft spokesman Jesse Verstraete had no immediate comment, but he
said the company would issue a statement shortly.
The company's proposal is close to what regulators called for in January
when they asked Microsoft to offer several browsers on Windows.
The ballot screen option is also backed by Norwegian mobile Internet
browser maker Opera Software ASA, which triggered the EU antitrust case
by complaining that Microsoft was unfairly using its power as the
dominant supplier of operating system software to squeeze out rivals.
Microsoft earlier suggested stripping Internet Explorer out of Windows
to sell it without any Web browsers at all in Europe. The EU rejected
this as giving no choice to the 5 percent of consumers who buy Windows
software in a stand-alone pack.
Most people buy Windows already installed on a computer assembled by
manufacturers such as Dell or HP.
The EU also said Microsoft has offered to share more information to
software developers who want to make products compatible with Windows
and Windows servers. It said these proposals "require further
investigation" before officials could decide on next steps.
Microsoft's proposals will be published on its Web site.
AOL Tries To Recapture That Startup Feeling
It might seem an odd move for a company that relies on money from
advertising. Yet AOL is reducing the number of ads it shows on its home
page and some other Web sites it runs.
The maneuver is one of the changes new CEO Tim Armstrong, 38, has
brought to the long-struggling Internet company since he took over AOL
in April. The former Google Inc. executive was hired to recharge AOL and
lead its spinoff from Time Warner Inc., undoing a legendarily disastrous
deal.
To prepare for AOL's rebirth as an independent company later in the
year, Armstrong and other executives say they are trying to recapture
elements of the culture AOL had when it was a startup - back when it was
America Online and on its way to becoming the dominant provider of
dial-up Internet access.
These days, AOL is focused on getting revenue from ads it sells for its
own Web sites, like celebrity gossip blog TMZ, and for third-party
sites, while the dial-up business slowly evaporates (though it still has
6 million subscribers). It's been a profitable formula, but revenue has
been falling: In the first quarter, sales fell 23 percent to $867 million.
With 7,000 employees spread around the world, it's a stretch to think
AOL can feel like a Silicon Valley startup, with employees whizzing down
the halls on skinny scooters. But Armstrong says certain decisions -
like getting rid of some advertisements - will alter AOL's culture and
help it regain favor.
"I think AOL's return to higher prominence in terms of being an Internet
leader is purely dependent on the work that we do here," the tall,
affable Armstrong said in an interview.
For instance, he said, pulling back some ads - a step that reduced
clutter on AOL pages and made them load faster - showed that consumers
were the company's first priority, given that the move could sacrifice
some revenue.
"We are on a long journey and sometimes you do have to make short-term
trade-offs for that long-term gain," said AOL's new head of advertising,
Jeff Levick. He also came from Google, where Armstrong oversaw the
company's North and South American advertising operations.
In some cases, reducing ads might not even hurt revenue. Armstrong said
that when AOL cut some ads from its MapQuest site, traffic rose while
the company made the same amount of money off the remaining ads, which
could each get more attention.
Another goal of Armstrong's is to speed AOL's ability to innovate. He's
made Tuesdays into "product meeting days," with teams behind several
different AOL products or services - say, AOL Autos or the company's
e-mail service - discussing ideas with executives. Armstrong says
lower-level employees now get a greater say in these sessions.
"We don't always need management to present what's happening at the
company," he said.
The impending spinoff from Time Warner also appears to be changing the
atmosphere. Bill Wilson, head of the company's MediaGlow unit, which
includes Web sites and blogs such as WalletPop and Engadget, said
employees are beginning to feel they have more influence over AOL's
destiny.
"That's much harder in a conglomerate than in a focused company," he said.
Even so, it remains to be seen how far enthusiasm and a new focus can
carry AOL. The company is in a fierce battle for Internet users with the
likes of Google and Yahoo Inc., not to mention upstarts such as Facebook
and Twitter.
Last fall, AOL tried to innovate by creating a way for users to view
outside content, including e-mail from Yahoo and Google, from within the
bounds of AOL.com. But the brand is not widely associated with what's new
and cool online.
Its Web sites do get plenty of traffic, though: AOL's various Web
properties averaged about 107 million unique U.S. visitors each month
during the second quarter. That ranked fourth behind Google, Yahoo and
Microsoft Corp.
"They've got opportunities," said David Joyce, an analyst with Miller
Tabak & Co. "So let's see what they make of it."
Laptop Prices Dip Under $300 in the US
Laptops are closing the price gap on less-powerful netbooks, with
retailers delivering fully equipped systems for under US$300 as part of
promotional offers.
Wal-Mart will start offering limited quantities of a fully loaded Compaq
laptop for $298 starting July 26, according to an entry on Wal-Mart's
Checkoutblog site.
The laptop being offered is a Compaq Presario CQ60-419WM from
Hewlett-Packard, which is powered by Advanced Micro Devices' Sempron
SI-42 processor running at 2.1GHz. The laptop comes with Windows Vista
and includes a 15.6-inch screen, 3GB of RAM, a 160GB hard drive and
Nvidia's GeForce 8200M integrated graphics. It also includes a DVD-RW
drive, according to specifications provided by HP.
For such a low price, the laptop is packed with features and could run
out of stock quickly. "We expect this one will be quite popular," wrote
a Wal-Mart official going by the name of Ryan in the blog entry.
Wal-Mart didn't clarify whether the offering would be in-store or
online, and the retailer didn't immediately return requests for comment.
The offer follows a move earlier this week by Best Buy to offer an Acer
laptop with a 15.6-inch screen for $299. The offer was later pulled
after Best Buy ran out of stock, according to a report in CNET. The laptop
was powered by a single-core AMD Athlon 64 running at 2.0GHz and ran
Windows Vista. The laptop also included 2GB of RAM and a 160GB hard drive.
By comparison, the cheapest netbook on Wal-Mart's online store is
available for $238 and is less powerful than the Compaq laptop. The Asus
Eee PC900HD includes an 8.9-inch screen and runs on an Intel Atom N270
at 1.6GHz. It includes 512MB of RAM and a 160GB hard drive and comes
with Windows XP.
Mainstream laptop prices have dipped under the $300 mark just a few
times, including in 2007, when Toshiba offered a laptop for $299. Most
of the mainstream laptops listed on Wal-Mart's site today are priced
over $350.
Wal-Mart also plans to add a "very cool Acer laptop" with an eight-hour
battery life over the next few days, according to the company. It also
plans to add a HP netbook.
Wal-Mart Woos Laptop Shoppers
Wal-Mart Stores Inc has expanded its laptop selection by 40 percent and
will be aggressive in pricing the computers and the accessories to go
with them as the discount retailer looks to win sales from frugal
back-to-school shoppers.
Starting this Sunday, Wal-Mart will begin selling an exclusive Compaq
Presario notebook computer that it developed in partnership with
Hewlett-Packard Co for $298. A similar unit currently sells at Wal-Mart
for $548.
"We think that that's a screaming value," said Gary Severson, Wal-Mart
U.S.'s senior vice president of home entertainment, in an interview.
"You're going to see us focus dramatically not only on price, but the
value for that price."
The Presario notebook will be selling at a price that would normally
purchase a less-capable netbook laptop.
Retailers have started the back-to-school shopping season on shaky
ground as consumers show an unwillingness to spend on anything but basic
goods.
According to a National Retail Federation survey, the average family
with children in kindergarten through 12th grade plans to spend 7.7
percent less on school gear this year than a year ago.
One bright spot in the survey was consumer electronics, where students
plan to spend more. In addition, nearly 75 percent of respondents said
they intend to shop at a discount stores for their new school purchases.
Wal-Mart is looking at the back-to-school season as a chance to showcase
its expanded selection of notebook and netbook computers, with Severson
saying laptops are becoming a staple item for students of all ages.
"We think that this year is really the opportunity for us to establish
in laptops," Severson said.
To gain leadership, Wal-Mart is following tactics it used to become a
major player in flat screen TVs -- expanding its selection of name
brands while trying to beat the competition on price.
Wal-Mart has already started its back-to-school push in earnest and is
offering Dell Inspiron laptops for $398 in colors ranging from pink to
purple to aqua.
The retailer also stocked accessories to match the colorful laptops,
like $60 Western Digital hard drives and $25 Logitech cordless optical
mice in black, blue, pink and red.
Wal-Mart said the Dell offering was a popular one, and it expects a
similar response for the Compaq Presario that goes on sale July 26. It
will have 3 gigabytes of memory, a 160 gigabyte hard drive, and it will
come pre-loaded with Microsoft Corp's Windows Vista operating system.
On Sunday, Wal-Mart will also cut the price of an Acer laptop with an
8-hour battery by $50 to $548. The computer has 3 gigabytes of memory, a
320 gigabyte hard drive and qualifies for a free upgrade to the Windows
7 operating system when it is released.
Wal-Mart will unveil more offerings during the summer, like a mini
netbook by Hewlett-Packard and a Dell laptop with 4 gigabytes of memory
and a 500 gigabyte hard drive.
"There's no question that our customer is shifting from a desktop
solution to a portable laptop solution," Severson said.
He also said Wal-Mart views low-cost netbooks as a "growth" category.
Netbooks, the bare-bones PCs, generally sell for $300 to $400, but
prices are dropping as new offerings flood the market and wireless
carriers offer subsidies with the purchase of a data plan.
Severson said Wal-Mart is looking at ways to offer shoppers deals on
netbooks that come bundled with a wireless plan.
"We're having conversations with carriers and with the hardware
manufacturers around that, and are really trying to find where that
great value sweet spot is," he said.
While some customers are attracted to netbooks by their low prices,
Severson said they do not always realize its capabilities are limited
compared with a notebook computer.
"There is an education process that has to happen with the customer, and
we're working on how we can improve that because there is a confusion
factor," he said.
This back-to-school season marks the first one without consumer
electronics retailer Circuit City, which closed its stores earlier this
year. Retailers including Wal-Mart, Best Buy Co Inc and Amazon.com
are now battling to win the business of its former shoppers.
Windows 7 Released to Manufacturing
After months of testing, telemetry, and trials - and leaked builds and
gossip galore - Microsoft has finally released Windows 7 to manufacturing.
Release to manufacturing, or RTM, is the final build of the operating
system before general release and general availability for consumers on
October 22. The official sign-off was at 4:40 PM, a quirky time
coinciding with the keynote speech at an internal sales and marketing
event.
Microsoft plans to make the RTM available to OEMs within the next two
days, while volume and enterprises licensees should see the code appear
on Microsoft's TechNet site on August 6, a list of dates which which
Microsoft made available late on Tuesday. Windows Server 2008 R2 also
reached the RTM status on Wednesday as well.
Microsoft notes that there aren't many big differences between the
Release Candidate and the RTM versions of Windows 7, with the only the
changes that were really necessary included in the final revision. Many of
those have been highlighted on the E7 blog and the Windows team blog (such
as the recent post on the changes to ClearType.
These changes aren't ones most consumers will notice, and you shouldn't
expect dramatic changes in performance, although the team has been
making small but steady improvements in performance ever since the
operating system first started running on real-world hardware, according
to Mike Angiulo, manager of the product planning and PC ecosystem team
for Microsoft.
Web sites and chat boards worldwide have been aflutter with leaked
internal builds of the OS for the past six months, but the Internet echo
chamber has been turned to high volume in the past few weeks.
In recent months, enthusiasts have been carefully studying each leaked
version's "build number," the string of numbers and letters that
indicates when a build was assembled and which exact version it is.
Several purported final builds carrying 7600-series strings were leaked,
eventually prompting Microsoft to officially deny the rumors that Windows 7
had gone gold. For the record, the final build of Windows 7 and Windows
Server 2008 RTM will both be 7600, with Windows 7's RTM build known as
7600.16385.
Finishing off the operating system doesn't mean Microsoft's engineering
division can kick back and relax, however. "My team is kicking into high
gear!" Angiulo said. "My team is on site at the manufacturing sites of
all the partners, making sure that that very, very final tests - as
they're putting their final system images together - are high performance.
We go into on-call beeper mode with anything that's related to the
manufacturing process."
In other words, the job's not quite over for MS engineers, who will
spend the next few months ensuring that drivers, Device Stage-specific
icons, and especially sensitive applications like antivirus tools will
work smoothly. This should lead to a better out-of-box experience for
consumers, the company hopes, with computers coming with special icons
already pinned in place and software installed and running smoothly.
Microsoft has already made great progress on this front, claiming to be
way ahead of where Vista was at this point in terms of partner support.
The 64-billion dollar question, however, is one of bit depth: Will OEMs
and consumers opt for the 64-bit version or stick with the 32-bit one?
Vista customers primarily use the 32-bit version of the operating
system, a term that designates the maximum length of the "words" the
computer uses. Linux and the Mac OS come in 64-bit flavors, which allow
an OS to address more memory and improve performance.
Windows has been available in 64-bit versions for years, yet adoption
has been slow, primarily due to fears of driver incompatibility.
Microsoft expects the mainstream versions of Windows 7 to be 64-bit,
Angiulo said, although the Starter edition will be exclusively 32-bit, and
netbooks based on slower chips like the Intel Atom will probably ship with
a 32-bit OS.
Microsoft Outlines Upgrade Paths to Windows 7
Microsoft on Tuesday detailed upgrade paths from old Windows editions to
its upcoming Windows 7 OS, saying that Europeans will not be able to
directly upgrade from Windows Vista to Windows 7.
Microsoft is expected to ship special versions of Windows 7 to European
customers, but the versions will need a clean install on PCs, according to
a blog entry on Microsoft's Web site. The software giant has released
special editions of Windows 7 in Europe including Windows 7 E, which lacks
a browser, and Windows 7 N, which lacks a browser and media player
technologies. Windows 7 is scheduled for a worldwide launch on October 22.
The company released Windows 7 E editions - including Premium,
Professional, Ultimate and Starter editions - to comply with the
European Commission's antitrust ruling against the company. However, the
commission panned Microsoft's decision to strip the browser from
Windows 7 E, saying that instead of providing more choice, Microsoft
appeared to be providing less choice.
Users in other parts of the world will be able to upgrade directly from
Windows Vista to Windows 7. However, Microsoft isn't allowing upgrades
from Windows 7 Release Candidate or Windows XP, according to a document
outlining OS upgrade paths for users worldwide. Nor are direct upgrades
allowed from Windows NT Server 4.0, Windows 2000 Server, Windows Server
2003, Windows Server 2008 or Windows Server 2008 R2.
Microsoft last week started taking pre-orders for the European editions
of Windows 7 at discounted rates. The OS flew off the shelves, causing
Microsoft's online store to crash. The OS also reached the top-selling
list of online stores in Europe.
Microsoft may not be providing a direct upgrade path, but it is
providing an option for users to select and install a preferred browser
from external storage devices like USB thumbdrives or separate DVDs. It
is also providing a tool called Windows Easy Transfer
to help users transfer program settings and data from old operating
systems to Windows 7.
A request made through Microsoft's external public relations company for
additional comment regarding the upgrade paths was not answered Tuesday
afternoon.
=~=~=~=
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