Hand-rolling a CP/M machine

On 24 Apr 2007 at 14:29, Ethan Dicks wrote: Basically 8085 timing with a Z80 instruction set in CMOS (has a low- power "sleep" mode). I've got a few (maybe 20) of the 2.5 MHz parts. Love to get my hands on a couple of the 4 MHz parts. There was an article in one of the mags about retrofitting one into a CompuPro 85/88 board. There are some signal inversions and a few timing issues requiring some extra glue, but it's an interesting way to upgrade an 8085 box to run Z80 code. There is an extra configuration port at (IIRC) I/O address 0bbh, so you have to be careful to avoid collisions with existing port usage. The good news is that said port responds only on OTI/INI instructions and not the 8085-style OUT and IN (immediate port address) instructions. I've had lousy luck getting one to work with an 8202 DRAM controller, however. Runs fine from ROM and gets very sick the moment it sets a toe into DRAM. One of these days, I'll hang a logic analyzer on it and figure out if it's fixable. Cheers, Chuck