This is pretty obscure, and super old sk00l, but I am completely fascinated. This guy found a disk that was readable by both C64 and IBM PC – quite a rare find indeed…
This diskette has officially blown my mind.
This is the very first time I have ever seen something like this. The data for the IBM program takes up more than 160KB as evidenced by a DIR. The C64 1541 drive is a single-sided drive; IBM’s is double-sided. Based on all this, we can deduce how this diskette is structured and why:
– The IBM version of the game required more than 160KB (ie. needed more than one side of a disk), probably because it has a set of files for CGA/Herc (4/2 colors) and another for EGA/Tandy (16 colors) and either set will fit in 160K but both won’t
– The C64 version required around 80K, based on the fact that every other track is unreadable by an IBM drive
– The publisher had the requirement of using only a single disk to save on packaging and media costs
– Not wanting to limit the game to either CGA or EGA, someone at Artech (the developer) built the format of this diskette BY HAND so that DOS would not step on the C64 tracks, and somehow the C64 would also read/boot the disk
I don’t know how the C64 portion boots since track 0 sector 0 looks like a DOS boot sector, but quick research shows that C64 disks keep their index on track 18. If anyone knows how C64 disks are read and boot, I’d love to know.