yup, switchable so that CP/M can run Z80. On Sat, May 30, 2020 at 6:32 AM William stewart <[email protected]> wrote:
> Stephen, > Are you suggesting a swap of the 8085? > > Sent from my iPhone > > On May 29, 2020, at 7:46 AM, Stephen Adolph <[email protected]> wrote: > > Reviving this thread. > Now that we have a solid CP/M application written in 8080, there should be > a way to boot into CP/M using the NSC800. > I dropped this project some time back but it is time to revive it, as a > processor swap would be a cleaner way to expanding the CP/M application > universe for the M100. > > > > On Thu, Jul 11, 2019 at 10:30 AM Stephen Adolph <[email protected]> > wrote: > >> 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. >> >> >> >>
