Motivated by 2 things 1) discovery of the NSC800 Z80 processor that is 80C85 like 2) continuing to work in the direcition of CP/M 3) and recalling that there are 5MHz 80C85 parts out there..
I started to work on a dual CPU card for M100 that enables a couple of things; - standard 2.5MHz 80C85 operation (default) - switchable clock for 80C85, supporting 5MHz - switchable CPU enabling NSC800 at 2.5 MHz. Board is done and heading to the fab. VHDL is mostly done. I don't expect this board will be wildly popular but maybe it has some interest Double speed M100 seems interesting on it's own, let alone being able to support Z80 CP/M applications. Any interest? I have purchased material to make 5 of these. A few more comments. - to install this board you need to remove the 80C85. that's some effort to do - to run at 5MHz you need to upgrade the 81C55 to a 5MHz version. That's also some effort. - NSC800 runs about 5$ on ebay. - fast 80C85 can be had for under 5$. - fast 81C55 can be had for under 5$. - to run at 5MHz you might also find you need a faster main ROM, and faster RAM. TBD on that; will advise after I do some testing.
