2.3: CD-ROM Optimizations
This chapter details some of the usual tricks and techniques for optimizing the CD-ROM image of your project, to help improve load times and possibly helps reduce wear on the CD-ROM pickup in the console itself.
Data Ordering
Data in a CD-ROM is normally stored in a linear fashion and no file is ever fragmented, somewhat similar to a record. A common method of improving loading performance is by ordering files in a manner that frequently used files are placed close together. This reduces the amount of time it takes to seek between files.
Data ordering is typically controlled in BUILDCD and MKPSXISO by when in the script the file is specified. As in, the first file specified will be the closest to the very beginning of the disc wheras a file specified last will be placed at the very end of the file system.
If your project loads a set of files sequentially, it is optimal to order the files in the same manner. That way, the optical pickup does not have to seek much to read the next file (ie. file1 -> file2 -> file3).
Think of seeking as like having to lift the needle of the turntable to select a different piece of music on the record to play.
Single Reads are Faster
Much like a turntable, CD-ROM drives perform best when reading big chunks of data linearly. This same principle also applies on the PS1. Therefore, loading one big file in a single read operation is significantly faster than loading several smaller files from CD-ROM.
This method of optimization can be accomplished by developing a very simple file archive format just for consolidating several small files such as texture images into one large file. This may be described in future chapters.
Place Streaming Data Last
It is ideal to place streaming data such as CD-XA and STR video files after game data. This way, the seeking distance when loading game files will be focussed in the innermost part of the disc. Having an XA stream or STR video file in between such files will add a considerable amount on seek distance as such files are usually quite large.
Naturally, CD Audio tracks cannot be placed within a data track and is always placed the end of the file system, due to the way how CDs and tracks work.
