The Quest for the Ultimate Display System
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∫ The Quest for the ∫
∫ Ultimate Display System ∫
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∫ by ∫
∫ Steve Gibson ∫
∫ GIBSON RESEARCH CORPORATION ∫
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∫ Portions of this text originally appeared in Steve's ∫
∫ InfoWorld Magazine TechTalk Column. ∫
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I remember those simple days not so long ago when a purchaser of a brand new IBM Personal Computer had only one choice to make when it came to choosing the display system for his computer. Blessedly, the only choice to be made back then was between either a monochrome display and adpater, the so-called MDA solution, or a color screen and adapter, and CGA route. Needless to say, things are not so simple or straightforward these days! There are so many choices and options open to a purchaser or upgrader of a PC that I'd be crazy to even ATTEMPT to offer any clarification or guidance.
Okay, so call me crazy. It's time to choose the display subsystem for Steve's Dream Machine and I've got some real surprises in store for you this time! I've spent most of the past six weeks (when I haven't been reconfiguring my system between VM/386, Desqview, and Omniview) researching, probing, and digging for the best possible contemporary display solution for the least possible money.
Surprisingly, my research has uncovered some truly startling facts which I'll be sharing through the next few weeks as we explore THE DISPLAY SYSTEM FOR STEVE'S DREAM MACHINE. We'll see things like why the new 16-bit display adapters are generally not worth a dime more than their older 8-bit predecessors, how few, if any, VGA adapters on the market are REALLY register level compatible, and what risk that represents in light of IBM's unknowable future plans. We'll see what extra display memory DOESN'T buy for you because many of the manufacturer's device drivers don't even use it, why the highest resolution modes can be much more trouble than they're worth, and what NOT to pay for a great high resolution display.
Given the incredible variety of available choices (not at all like in the old days) it may surprise you to know that I have found ONE set of choices which delivers far more bang for the buck than any other! In order to give these conclusions a proper perspective, let's first step back for a moment to review the technological fundamentals and constraints which give our decision meaning. Then we'll see where we've been and where we're going.
No matter what style of display screen and interface adapter is in use, several fundamentals always apply. In the first place, the image displayed by a CRT screen is not at all the static image which it appears to be. In fact, there's never really an image being displayed on the screen at all! If you were to photograph a computer display screen with a high speed camera you'd only see a single bright dot of light rather than an entire image.
The illusion of a screen full of information is created with the aid of some incredible technology. The screen is actually painted by a single madly whizzing dot of light which traces successive horizontal lines across and down the face of the display tube. When I say "madly whizzing" I'm not exaggerating because a typical CRT screen paints horizontal scan lines on its face at the rate of 350,000 inches per second, which is 20,000 miles per hour! This furious speed is required in order to fool our eyes into believing that the entire image is being continuously displayed when in fact it's mostly NOT being displayed!
A typical display screen consists of about 450 of these horizontally scanned lines, each of which must be redrawn or "refreshed" at least every sixtieth of a second. This means scanning across 27,000 lines per second, every second. If this is not done our eye will perceive that the lines are not being continuously illuminated and the illusion we've tried so hard to achieve will fail.
As the single dot of light traces its furious course it changes color thus tracing out the full screen image which is stored in the display adapter's DISPLAY REFRESH MEMORY. On a monochrome screen which is limited to displaying a single color, the dot of light varies in brightness only, whereas a color display system allows the dot's instantaneous color to be varied as well.
So we're left with a number of important concepts: In order to eliminate the overall "refresh flicker" of a display screen, the entire screen must be redrawn or repainted approximately 60 times each second. Since the scanning dot traces lines from left to right as it moves more slowly vertically from the top of the screen down, the downward motion is referred to as the screen's Vertical Refresh Frequency and the very rapid horizontal left to right scanning is referred to as the display's Horizontal Refresh Rate.
The Display System Adventure Continues
So we've seen that the display screens of our computers rely entirely upon our eye's persistence of vision to assemble the illusion of an image on the screen. Each dot which composes the display must be redrawn, or refreshed, at least sixty times each second in order to appear continuously illuminated. Now we'll examine the evolution of our display screens, giving some perspective to where we've been and where we are today.
The original Color Graphics Adapter (CGA) traces its ancestry directly from commercial television. Commercial TV refreshes its screen exactly 60 times per second with a horizontal scanning frequency of 15,750 cycles per second. The IBM CGA display utilizes this timing to support the images it generates. The total number of horizontal scanning lines traced onto the screen by a CGA system can be determined simply by calculating how many horizontal lines are scanned out during one vertical scan. Since the screen is scanned vertically 60 times per second, we divide 15,750 by 60 to yield the horizontal line count of 262. Two hundred of these scan lines are used to display actual image data, with the balance used to illuminate the CGA screen's border region.
As we all remember, the CGA was not known for producing highly legible text (for some it's not yet a memory). The prime determiner of text quality is the number of individual pixel dots which are available to display individual characters. Dividing 200 total image lines by 25 lines of text yields just 8 scanning lines available per text line. Then since the CGA adapter was able to display 640 dots across a horizontal line, dividing this by 80 characters per line yields 8 pixel dots horizontally per character.
So CGA technology yielded a budget of 8 by 8 pixels per character. Since it is necessary to separate characters by at least one blank pixel, and since characters are taller than they are wide, CGA characters were designed to fit within a rectangle of dots 5 wide by 7 dots high. If you have a few moments to spare some time with some graph paper, try designing an entire upper and lower case alphabet where each character fits within a 5 by 7 pixel cell. It's not simple, and there is no really great solution.
Driven by the concern that serious business computer users would be very unhappy with the appearance of CGA text, IBM decided to provide a better text display alternative. The Monochrome Display Adapter (MDA) was the result. In order to deliver more legible characters, more pixels are required both horizontally and vertically. Where the CGA fits 5 by 7 characters into 8 by 8 "cells," the IBM monochrome display provides much higher resolution: 7 by 9 characters within a 9 by 14 space.
Changing the character resolution from 5 by 7 to 7 by 9 results in a tremendous improvement in character legibility, and a 2- pixel horizontal inter-character spacing with a 5-pixel vertical spacing leaves the display's characters feeling quite uncrowded.
The question is, where did IBM get all those extra scan-lines? 25 lines of text with 14 scan-lines per line means a total of 350 active scan lines compared to the CGA's 200! The scan-line count can be increased by increasing the horizontal scan frequency so that more lines are scanned per second, or by decreasing the overall vertical refresh rate thus allowing more time to scan the horizontal lines.
IBM did both of these things to create the MDA standard. The MDA refreshes its screen at only 50 cycles per second with a horizontal scan rate of 18,432 hertz. Now, dividing 18,432 by 50 yields about 368 scan lines. Since 350 of these are required for text display, the MDA is not able to display a border.
But how can IBM refresh the MDA screen at only 50 cycles per second if we begin noticing a flicker as refresh frequencies fall below 60 cycles per second? IBM compensated for our lack of vision persistence by designing a highly persistent green phosphor into their monochrome display. Many people immediately noticed a "smeary" effect whenever the IBM monochrome display scrolled text. This smearing was created by the use of a long persistence phosphor which continued to glow long after the screen's electron beam stopped refreshing the region.
If you've ever noticed an annoying continuous flicker from an inexpensive clone monochrome display, now you know why. Most clone monochrome displays use less expensive standard short or medium-length phosphors... which are inadequate for masking the very noticeable effects of the MDA's lower refresh rate. Also, since the flicker-perception phenomenon is extremely subjective, many people perceive flicker where others don't. I've learned that I don't see flicker where other people are being driven nuts by it.
With an understanding of the interactions of horizontal and vertical scan rates and display resolution we're ready to explore the EGA, VGA and multisync technologies.
The role of Hercules Graphics, and the evolution of the EGA
We've seen how IBM designed their MDA monochrome display system to deliver extremely well-formed characters by increasing the display's horizontal scanning rate and decreasing the vertical refresh rate. Before continuing our discussion of EGA, VGA, and multisynchronous monitors, it's important to understand another quite well established and significant display standard, Hercules.
Perhaps IBM simply overlooked the idea of monochrome graphics altogether, or underestimated the demand for the display of graphic information. More likely though, IBM felt that the word- processing market toward which they were targeting their monochrome display system had no need to display graphics. How could IBM, or anyone for that matter, have anticipated the phenomenal effect Lotus' 123 spreadsheet product would have upon the IBM compatible market?
While columns of numbers are indeed informative, the ability to graphically display, correlate, and view the results of spreadsheet calculations is extremely useful. The folks at Hercules Computer quickly recognized this and designed a wonderful solution which, with the early support of Lotus, became a solid standard.
Since the Hercules high resolution mode was designed to operate with an IBM or compatible monochrome monitor, at a horizontal sweep rate of 18,432 cycles per second and a refresh frequency of (only) 50 hertz, it could directly leverage the extremely high resolution which IBM had designed into their monochrome text system. The Hercules monochrome display resolution of 720 by 350 pixels made the CGA's 640 by 200 look quite sad when compared side by side, and suddenly people could have both readable text and great looking graphics at the same time and from a single system.
IBM's next move demonstrated that they'd been listening to their user's complaints about the low resolution of the CGA standard. They were also watching the guys at Hercules make money like crazy and were attempting to serve the always mixed blessing requirements of full backwards compatibility. The IBM Enhanced Graphics Display was IBM's second generation solution, and it rapidly became a new standard for the industry.
By recognizing the CGA system's crying need for better text, IBM saw that it had to crank up the scan line count to something more like their monochrome display; however, since full-color long persistence phosphor monitors are barely affordable by small countries, IBM knew that it couldn't play the trick of getting the scan line count up by lowering the system's overall refresh rate below 60 cycles per second. The only alternative was to push the system's horizontal scanning frequency higher than the monochrome system's.
This would mean that their new EGA display system would not be backwards compatible to the existing installed base of 200 scan line resolution CGA software. (The non-optimal solution crimes which are continually committed in the name of backwards compatibility is probably my single biggest pet peeve. It directly accounts for the unprogrammablity of the Intel microprocessor instruction set!) So, in order to achieve CGA compatibility from their new EGA system, IBM invented the "bi-synchronous" display system.
By inverting the polarity of the EGA monitor's Vertical Synchronization signal, the EGA adapter is actually able to switch the EGA monitor between two separate modes: The CGA's horizontal sweep rate of 15,750 cycles per second and the newly invented EGA horizontal rate of 21,800 cycles per second. The 15,750 hertz rate yields a CGA software compatible resolution of 200 lines, while the 21,800 hertz rate results in a full Hercules-type resolution of 350 lines. In EGA graphics mode, this results in a significant, Hercules-similar resolution of 640 by 350 pixels.
Since IBM seems determined not to kick the horizontal resolution of these systems up above 640 pixels, we don't quite get the full character separation beauty of MDA and Hercules text. On the other hand, the EGA's character resolution budget of 8 by 14 pixels is significantly better than the CGA budget of 8 by 8 and allows lower case characters with descending tails like "g," "p," "q," and "y" to be imaged cleanly. The EGA's resulting well-formed characters made most people happy.
The EGA's final addition to the CGA standard was the provision for additional colors. Where the CGA display could display 8 colors in either of two intensities, bright or dim, the EGA display, when operating in EGA mode, allowed each of its three primary colors, Red, Green, and Blue, to be mixed together in any of four intensities. Therefore 4 times 4 times 4, or 64 total colors could be displayed by IBM's EGA display. Though technology has passed the EGA monitor by, it represented an adequate, backward compatible, unification of the CGA, MDA, and Hercules standards.
IBM's recognition of the EGA's shortcomings with the creation of the VGA "standard"
On our journey toward the goal of selecting the best possible display system for the least possible money for Steve's Dream Machine, we've traced the evolution of IBM compatible display system technology from the original CGA and MDA standards through the development of the Hercules and EGA standards. IBM's announcement of its new generation PS/2 machines offers yet another display system to "the standard" throne. Oddly named after the integrated circuit chip which implements it, the Video Graphics Array, or VGA, has provided enough new cleverness and innovation to displace the prior EGA standard.
With graphic user interfaces gaining ever more market recognition and IBM's own OS/2 Presentation Manager on the horizon, IBM needed to push their graphics resolution offering above the EGA's 640 by 350. At the same time, IBM wished to further enhance the system's color capabilities, probably to further differentiate itself from Apple Computer's monochrome Macintosh products and to better compete with Apple's newer colorful Mac II. To further confuse things, this was all happening at a time when IBM was determined to lower its manufacturing costs.
While the EGA display was innovative with its split-personality dual-frequency horizontal sweep rate in order to deliver both 350 line vertical resolution without sacrificing 200 line CGA compatibility, is was more expensive to manufacture than IBM was now happy with. IBM made a brilliant move in their VGA system which completely eliminated the need for the expensive frequency changing display while actually enhancing the appearance of older CGA-style text and graphics.
The VGA's fixed horizontal sweep rate of 31,500 cycles per second offers several wonderfully clever savings. In the first place, dividing the horizontal rate of 31,500 hertz by the 60 cycle vertical rate yields 525 total horizontal lines scannable during one screen. This high scan line count delivers even better legibility from VGA text which now has a text character pixel budget of 8 by 16, while the EGA's barely adequate high resolution line count of 350 jumps up to a very respectable 480. The excess line count (the difference between the 525 total and the 480 used) even allows a tidy 1/4 inch border in all modes.
The VGA's cleverness stems from two additional things which IBM did in order to deliver backward compatibility to the CGA and VGA. The VGA monitor's very fast horizontal scan rate put IBM in the enviable position of actually having, in some cases, too many scan lines, rather than too few. So in such cases IBM slightly INCREASES the vertical refresh rate (to above 60 hertz) in order to trim back on the number of lines displayed when they need fewer.
Secondly, rather than slowing the display's HORIZONTAL rate drastically down to the CGA's 15,750 cycles, in order to deliver just 200 horizontal scan lines, the VGA raises its VERTICAL rate just slightly up to 70 hertz which yields 400 scan lines. Then a clever double-scanning approach is used to emulate the CGA's 200 line mode. Double scanning simply repeats each of the CGA's lines twice and results in a higher resolution appearance while maintaining complete software backward compatibility.
The only remaining "tweak" required involves keeping the VGA's displayed screen height constant which the IBM VGA monitor achieves by sensing the polarity of the Vertical Synchronization signal sent to it by the VGA adapter. The monitor uses the Vertical Sync signal polarity to adjust the spacing between successive scan lines so that the VGA's image is kept almost uniformly sized throughout the increasing jungle of new, old, and older display modes.
Thus the VGA system scans 350, 400, and 480 lines to achieve CGA, EGA, and VGA compatible display modes while leaving the horizontal scanning rate set to a constant 31,500 hertz and only tweaking the vertical refresh rate between a happy 60 and 70 cycles per second. The result is a simpler and far less expensive VGA monitor which exceeds the EGA's capabilities and delivers far cleaner CGA emulation.
The other major change presented by the VGA system is an expansion of the system's color capabilities. The original CGA monitor utilized one signal each for Red, Blue, and Green colors, and an additional single signal for intensity which delivered 16 total possible colors. The EGA expanded upon this by providing two signals each for the Red, Green, and Blue colors, thus delivering four intensities of each color, with 64 color mixtures possible. The VGA's color system operates in an ANALOG rather than DIGITAL fashion where varying voltages, rather than ON/OFF signals are provided for each color for mixing. Software and memory limitations pare the resulting infinite color possibilities down to a maximum of 256 colors chosen from a total palette of 262,144 in some display modes.
NEC's Brilliant Creation of the Multisync, and 800 by 600 Resolution Graphics
We've taken a detailed look at the evolution of IBM compatible display systems, focussing almost exclusively upon the multitude of standards which have first been set then soon superseded by IBM. We've seen that the various display adapters have always been "tightly coupled" to their display monitors and have frequently employed fancy "kludge" solutions (like conditional inverting of synchronization signal polarities) when necessary to maintain backward compatibility to the multitude of prior standards.
Amid the wilderness created by the incredible array of vertical and horizontal scan rates, a solid alternative to the eternal IBM lock-step frenzy has arisen. Originally conceived by Nippon Electric Corporation (NEC) as an answer to just this problem, the so-called "multi-synchronous" display monitors are now selling in the hundreds of thousands for a very good reason.
In what could only be called a truly astounding leap of insight, the designers at NEC integrated the past and predicted the future when they invented their original NEC Multisync, a single unified display monitor solution for all adapter technologies past, present, and future. Rather than following IBM with yet another tightly coupled clone display monitor, NEC invented a single monitor which quietly displayed anything it might be handed by the system's display adapter. By accepting an unheard of range of vertical and horizontal synchronization frequencies, as well as both digital and analog RGB intensity signals, the NEC Multisync became virtually obsolescence-proof.
While IBM was busily requiring all of its EGA owners to completely scrap their "yesterday's solution," EGA monitors which would no longer be compatible with the VGA of today (and tomorrow?), and purchase the all new VGA displays, proud Multisync owners only needed to change their monitor's cable then flip a couple of switches at the rear of their displays. That's what I call truly brilliant engineering!
Of course it wasn't long until everyone else recognized NEC's brilliance and began cloning multisynchronous monitors like mad. Today's mail order ads are drenched in "generic multisynch-ness" because it's simply the right way to go.
However, there's something else which makes multisynching the right solution, and after extensive experimentation and comparison it has become an INFINITELY CRITICAL COMPONENT of Steve's Dream Machine: Support of the wonderful 800 x 600 pixel super high resolution modes which are now available from all state-of-the-art EGA and VGA display adapters.
Many of you will remember that Steve's Dream Machine and I have been holding onto monochrome display technology for dear life... looking to monitors such as the Wyse-700/Amdek-1280 and MDS Genius to provide the truly useful bit-mapped graphics resolution which is, and will be, required by today's and tomorrow's desktop publishing, MS Windows, and OS/2 Presentation Manager applications. Until many months of searching yielded the incredible, ultimate, adapter/monitor combination, I didn't believe that a color system could really deliver "truly useful" (and in fact wonderful) high resolution bit-mapped displays. It can. I'll tell you about the results of my quest, but first we need a bit more foundation...
It turns out that truly useful bit-mapped resolution requires stepping above even the VGA's new 640 by 480 resolution up to 800 by 600. By cranking the horizontal sync up to 35,100 and sneaking the vertical refresh just a tad below 60 hertz to about 56, any solid multisynchronous monitor can readily display 600 lines of 800 full color pixels per line.
There's something magical about the difference between 640 by 350, 640 by 480, and 800 by 600. It's a staggering difference. The prior two resolutions simply pale by comparison to 800 by 600. Trying to understand why things get so incredibly better as the resolutions are increased, I've decided that it's because the total pixel count increases with the PRODUCT of the horizontal and vertical resolutions. This is a powerful relationship. For example, on a screen with square resolution, the total pixel count would increase with the SQUARE of the screen's edge resolution, so a DOUBLING of edge resolution produces a QUADRUPLING of the total pixel count. Consequently the standard EGA resolution of 640 by 350 contains only 46% of the pixel count of 800 by 600, and even the VGA offers only 64%. 800 by 600 resolution delivers 156% of the VGA's pixel count.
So at this juncture we must leave IBM in the dust. Only enhanced EGA and VGA adapters are able to generate 800 by 600 pixels, and only multisynchronous displays can lock onto the extreme synchronization frequencies required for the delivery of this stunning and readily available resolution.
The Incredible SONY CDP-1302A... Steve's Dream Machine Monitor of Choice!
Having decided that Steve's Dream Machine monitor had to be multisynchronous in order to deliver the most resolution possible, the next obvious question was: Which one was the best? After staring endlessly at, and touching and feeling, just about every available candidate, I determined that no other monitor comes anywhere NEAR the quality of the Sony "Multiscan" CDP- 1302A. The Sony Multiscan is solidly entrenched as the Steve's Dream Machine video display monitor. After purchasing several, I couldn't be more pleased.
The single feature which distinguishes the CDP-1302A from the crowd, placing it heads and shoulders above the rest, is its image quality. Based upon Sony's legendary Trinitron color picture tube, the 1302A packs its primary red, blue, and green phosphors so closely together that white text actually looks white, rather than appearing as an ugly island of white fringed with red on one side, green on top, and blue on the other side.
Coming from the purely monochrome character coloring of monochrome displays as I did, I just wasn't willing to sacrifice text color purity for the sake of color. The Sony 1302A is the ONLY monitor in the industry which doesn't compromise text appearance for color capability. As I write this column with PC- Write, I'm staring at white text on a blue background. With my nose one inch from the screen, aside from being cross-eyed, I absolutely cannot see anything but white text on a blue background. No other monitor delivers this quality.
All contemporary color monitors operate through a process known as "SPATIAL COLOR MIXING." Though from a distance the screen appears smooth, homogeneous and continuous, it's actually composed of thousands of individual red, green, and blue phosphor regions. When the display's electron beams strike the phosphors from behind they fluoresce and glow in one of the three primary colors. By controlling the instantaneous voltages applied to each of the three electron beams at the back of the CRT, the red, green, and blue color phosphors in the region where the beams are striking are made to glow in proportionate brightness.
Our eyes, having somewhat limited resolution, don't see the individual red, green, and blue phosphors in the region, but instead spatially mix these colors into a single composite.
(It's rather incredible to realize then that the first thing our eyes do is to re-separate this composite color back into its red, green, and blue color levels since our eyes are built from light sensitive rods and cones which selectively respond only to red, green, and blue light!)
However, our eye's ability to convincingly spatially mix the screen's primary colors is a function of the center-to-center inter-color spacing, which is also known as the display's "DOT PITCH." Not only does the Sony have a significantly tighter dot pitch than any other large display in the industry (0.26 millimeters versus 0.31 or coarser for everyone else), but the Sony's Trinitron'ness seems inherently better suited to the job of helping our eyes to perform this mixing. It's almost as if the individual colors are being pre-mixed behind the screen before leaking out onto the tube's glass faceplate.
This dot pitch also means quite a lot when the monitor is being called upon to display higher resolution images. As the number of displayed pixels per inch begins to approach the number of phosphor dots per inch a strange interaction known as "SPATIAL FREQUENCY BEATING" occurs. You can most easily see this by drawing single pixel wide horizontal, vertical, or slanted black lines against a solid white background. Rather than appearing as black, the line's width is so much smaller than the surrounding illuminated pixels that these too-fat pixels bleed their colors into the supposedly black line, rendering a non-black dimly colored line. In practice, high resolution black on white applications such as desktop publishing end up appearing disturbingly multi-colored rather than pleasingly black on white. The 800 by 600 pixel resolution which multisync displays provide at no cost requires the dot pitch to be as tight as possible.
If you care about your eyes, I urge you to check into the Sony Multiscan CDP-1302A. This is NOT a place to compromise.
And the Paradise VGA Plus Card, the Ultimate VALUE in VGA Adapters
Having answered the burning question of the ultimate video monitor for Steve's Dream Machine with my enthusiastic ravings about the marvelous Sony CDP-1302A multiscan monitor, the final question to be answered for our display sub-system project is: What's the ultimate display adapter?
Determining the correct answer to this question was complicated substantially by the simple fact that the VGA marketplace is filled with an incredible degree of clutter, misdirection, overstatement, and outright lies. What you see and hear is almost always FAR FAR different from what you actually get. Wild claims made by VGA adapter manufacturers abound, the ads are largely full of baloney, and it's quite hard to really know what's true. It's also quite hard to know what really makes a DIFFERENCE in VGA adapters, so consequently even the normally shrewd buyer will wind up guessing.
As my research into VGA adapters progressed, and I learned more and more, I became increasingly upset by the state of affairs and committed a disproportionate amount of time and energy to the task of finding out what's REALLY going on. Getting underneath the covers to substantiate or debunk various claims required the creation of special benchmarking software to directly measure critical adapter parameters such as horizontal sweep rates, overall vertical refresh rates, and raw low-level adapter data bandwidths. What I discovered amazed me, and even though the results of this research may upset some significant players in the industry, I feel compelled to share what I found.
Since I don't want to tease you any more than necessary, I'm telling you right up front, here and now, that for my money, there is no adapter in the industry which delivers more overall value than the inexpensive, analog-only, 8-bit, incredible Paradise VGA Plus. Though the VGA Plus is currently in very short supply, being affected both by its own popularity as well as by our industry's current dynamic RAM shortage, it's an incredible value at its current street price of between $230 and $260.
I urge you not to purchase any other display adapter, VGA or otherwise, until you've heard me out. Though you might have to struggle and/or wait a while to find one, it'll be a decision you couldn't regret.
The various VGA adapters in the industry may be differentiated by applying the following tests and comparisons: raw low-level data bandwidth, companion software drivers, display monitor compatibility, IBM VGA register level compatibility, system- level hardware compatibility, and to a lesser degree backward compatibility with prior display standards.
Of all these characteristics, only video display compatibility and backward compatibility are obvious from the surface. Every other characteristic must be determined through actual use and testing. The only negative feature of the Paradise VGA Plus in this regard is it's total lack of support for the older digital- only monitors including the original IBM monochrome, CGA, and EGA displays. You won't be able to use the VGA Plus if you have one of these, though Paradise has stated that they will make a version of their card for sale to large OEM customers which will support both digital and analog monitors. This liability is shared by the Compaq and Video Seven Fastwrite and VRAM cards, so the Paradise is in good company. Of course this is no problem if you already own or intend to purchase any multisync monitor like Steve's dream monitor, the Sony CDP-1302A.
Almost every VGA adapter in the industry is a so-called "five- in-one" card. Five-in-one refers to MDA, CGA, Hercules, EGA, and VGA, and means that such cards can run virtually any software ever written to any of these major standards. The two notable exceptions are IBM and Compaq which lack support for the Hercules standard. Even though Compaq's VGA adapter utilizes the Paradise PVGA1A VGA chip, and could thus have easily implemented Hercules backwards compatibility and the useful extended resolutions as do the Paradise VGAs, Compaq chose not to bring these features to their purchasers, apparently preferring to remain more strictly IBM compatible. For this reason, and considering its high price, you'd have to really love the Compaq name in order to intelligently purchase Compaq's VGA adapter. It's a very nice adapter, but the Paradise Plus or Pro do more, cost less, and are otherwise identical, all being based upon the same VGA chip.
Display System Performance
It's hardly surprising that the single hottest issue in the VGA marketplace is performance. People want machines that don't slow them down, and since our video display screens are the windows into the souls of our machines, it's only natural to want a screen that can keep up with the CPU which lurks behind.
Being a performance fanatic myself, the first thing I did was to write a machine language benchmarking program to determine the fundamental raw machine-level data throughput of VGA adapters. As a low-end reference point, the true Blue IBM VGA adapter can accept text data at 569 Kbytes per second and graphics data, when in 640 by 480 resolution, at 592 Kbytes per second.
The IBM's raw text throughput of 569 Kbytes per second means that the entire 4000 byte text screen could be re-written 142 times per second. Since display screens are only displayed 60 to 70 times per second, anything faster than this is completely invisible and represents wasted performance. The point is, when displaying a 25 line by 80 column text screen, even the SLOWEST VGA card on the market (which the IBM VGA is) is twice faster than is even visible! Those "8 times faster" performance claims being made by several VGA competitors are based upon their card's text-mode throughput and are about as useful as a jet engine on a skateboard. I ignore such nonsense and the companies behind it.
However, what's true for text mode performance is not necessarily true for bit-mapped graphics. While an entire text screen is specified by just 4000 bytes of data, a 16-color 800 by 600 high resolution bit-mapped image requires 240,000 bytes of data! Even so, IBM's 592 Kbytes of graphics throughput can still paint an entire VGA image in four-tenths of one second. That really isn't bad.
So how do the other boards in the market compare? Well any board based upon the Tseng Labs (pronounced sang) chipset will deliver approximately IBM-grade performance. Tseng Labs based boards such as those from Genoa, Orchid, Sigma, STB, and Tecmar have throughputs of 591 Kbytes for text and 588 Kbytes for graphics, which is actually a bit slower than IBM. The advantage these boards have over the IBM is 5-in-1 backwards compatibility. Unfortunately, this comes with an expense of yawning performance. Several also utilize the Tseng Labs 1024 by 768 resolution mode. This requires display screen interlacing which halves the overall refresh rate and produces completely unacceptable display flicker when using Ventura or with Window's color mixing scheme known as dithering. One positive feature of these cards is their full support for the digital-only MDA, CGA, and EGA monitors, but since such monitors aren't state-of-the-art anyway, it would be a shame to choose a poor performing VGA adapter for the sake of running a poor performing display. For these reasons, I don't recommend Tseng Labs chip based VGA adapters.
Video Seven has been generating quite a lot of press attention lately with their FastWrite and VRAM VGA adapters. Having studied these boards at length with the hope that they would turn out to be real screamers, I have to admit to being less than fully impressed. I had significant hardware and software incompatibility problems with the FastWrite and VRAM boards and none with any others. Though I've heard that newer revisions have solved many of the earlier problems, I still feel shy toward them. Also, the incompatible way their video BIOS was designed prevents multitasking software from freely and properly switching tasks between various extended modes. This alone would keep me away from Video Seven's products.
However, it can't be denied that the Video Seven pair are uncontested winners when raw throughput alone is considered. In 640 x 480 mode, the FastWrite came in with 1.812 megabytes per second throughput, and the VRAM delivered a screaming 2.885 megabytes per second.
I was puzzled at this point because my favorite little Paradise Plus board, with its 1.139 megabytes per second throughput, just didn't SEEM to be any slower than the VRAM. It occurred to me that the board's raw throughput was being "watered down" by "software overhead" which would tend to equalize performance. After writing a new set of benchmarks to test performance THROUGH their respective Windows drivers, I found what I expected. Despite the fact that the VRAM board could accept raw bit-map data 153% faster than the Paradise Plus, the software overhead in the Windows drivers resulted in a performance difference of only 54%! When the application's own overhead was factored into this, the VRAM edge was even further blunted.
Due to architectural characteristics of the Paradise PVGA1A VGA chip, Paradise's 16-bit boards actually deliver NO MORE PERFORMANCE than the inexpensive 8-bit Paradise Plus, Steve's Dream Machine VGA board.
The Display System Series Loose Ends
Let's finish our study of the state of the art in IBM video display technology by tying down a variety of loose ends. As we've seen, my display adapter of choice is Paradise's 8-bit VGA Plus. Surprisingly, the architecture of the PVGA1A chip, which forms the heart of every VGA adapter from Paradise as well as the VGA systems produced by AST Research and Compaq, gains NOTHING from a 16-bit bus connector when the boards are used in their high resolution bit-mapped modes. This means that except for the additional memory on the Paradise VGA Pro board, there's absolutely no benefit to purchasing it over the less expensive 8-bit Paradise Plus. In fact, the temptation would then be to run the Pro card in its 256 color mode, but my benchmarks revealed that display performance suffers with higher color counts. This is hardly surprising since additional colors depend upon the use of additional memory which must be managed by the driving software.
After declaring the Sony "Multiscan" CDP-1302A to be today's ultimate video display, I was contacted by many competing vendors who wanted me to believe that their displays were better. As a result of entertaining several such possibilities I'm more certain now than ever that the Sony blows EVERYTHING else away.
As I acquire increasing experience with 800 by 600 resolution, which you get "free" when the Sony is paired with the Paradise VGA Plus, I'm becoming more and more certain that it's ultimately the best general purpose resolution. When running at 800 by 600 resolution, the Sony produces an active image area which is 10 inches wide by 7.5 inches tall. Dividing each of these lengths into the pixel resolution in that dimension yields exactly 80 pixels per inch IN EACH DIRECTION. This beats the Macintosh's 72 ppi resolution with a much larger screen while delivering the Macintosh's popular "square" pixels which are exactly as wide as they are tall. It's nice to have a system on which circles appear circular and squares really are square!
While I'm thinking about high resolution under Microsoft Windows, I really need to make sure you know about Micrografx's incredible Designer product. Designer feels to me like a highly evolved CAD package with an exquisite state-of-the-art Windows user interface. Using Designer has become fast and reflexive. It has that rare easy-to-learn feeling which results from several generations of detail polishing. While Designer completely answers my desire for the lightning fast creation of structured graphics, I've been surprised and delighted to find that several of my died-in-the-wool traditional "CAD freak" friends have completely switched to Designer after seeing me mouse my way around it. If you have any need for PC based drawing, I'd urge you to take a peek at Micrografx's Designer.
I'm addicted to Ventura Publisher for the creation of all manner of high grade hard copy, so the quality and legibility of Ventura's displayed image has profound importance for me. If you've been reading this column for long, you probably know that I tend toward perfectionism, always needing to get the most out of my system. So I've been irked by Ventura's three fixed display screen zoom factors. At each zoom setting the image is always either too small, leaving an unused "grey zone" to the right of the page's image, or too large, requiring a horizontal scroll to see everything.
Bitstream Inc. has developed and sells a fabulous technology called FONTWARE which generates any size and resolution of ultra-high-quality typefaces from a set of sophisticated typeface outline masters. Since the EGA's pixels aren't square, the EGA-compatible screen fonts which are shipped with Ventura aren't specifically tailored for 800 by 600 resolution. So I decided to used Bitstream's Fontware to regenerate an entirely new set of Ventura screen fonts with SQUARE pixels, and while I was at it, to choose a screen font resolution which would give me EXACTLY the Ventura zoomed sizes I wanted.
After some experimentation, I'm delighted to tell you that I now have exactly what I want from Ventura. By asking Bitstream's Fontware technology to rebuild Ventura's screen fonts at 100 by 100 pixel resolution the text of a standard 8.5 by 11 inch page with one inch margins EXACTLY FILLS the screen in Ventura's "normal" viewing mode with Ventura's mode selection icons displayed. The result is an incredibly clear and legible image in 800 by 600 resolution which puts the VGA's defacto 640 by 480 image to shame.
Micrografx can be contacted about Designer at (800) 272-3729 and Bitstream can tell you more about Fontware at (800) 522-3668.
- The End -
Copyright (c) 1989 by Steven M. Gibson
Laguna Hills, CA 92653
**ALL RIGHTS RESERVED **
