Guys I'm thinking of extending out 8088, 8086, 80286 and
80386 line of S-100 boards to include a 80486 board. The 80386 board was a
major hurdle for us hardware wise. The prototype and daughter RAM boards design
now feel fairly sound and should be available over the next few months.
While the 80486 would appear a small further hardware leap from the 80386 (and it is for 32 bit data), unfortunately Intel in their wisdom decided to handle 16 bit (and now 8 bit) data transfers differently to that on the 80386. Now the upper 16 or 8 byte/words and NOT shifted down to the lower data lines for 16 and 8 bit data transfers. You have to use external latches/buffers. This mounts to probably more 754LSXX IC's that a single board can accommodate. I think I could squeeze things using a few GAL's to eliminate a number of chips.
For programming them I would prefer not to use a high level language (the logic is simple, few chips). I was thinking of using something like PALASM. Could somebody direct me to a DOS/Windows version that I could get a run-time version. I see many references/write-ups but no actual run-time code.
BTW, with such an 80486 board even old 8 bit S-100 boards would be usable! (Like sticking a Lamborghini engine in a Volkswagen!).