right now it is dedicated. Philip and I have been discussing 'shared' operation, but hard cutover is what is working now.
On Fri, Jun 5, 2020 at 10:56 AM Joe Grubbs <[email protected]> wrote: > Sounds great Steve, keep us updated on this. You may have mentioned this > before, but do the two processors share the bus simultaneously, or is only > one or the other (like a Commodore 128)? > > ------------------------------ > *From:* M100 <[email protected]> on behalf of Stephen > Adolph <[email protected]> > *Sent:* Friday, June 5, 2020 10:44 AM > *To:* [email protected] <[email protected]> > *Subject:* Re: [M100] dual CPU project > > Hello all, > Interesting update. > So, I've been working on getting NSC800 AKA Z80 processor to work in the > M100 such that it can be used in CP/M as an alternative processor. > > Great news is that I now have a solution for actually running the M100 > using the NSC800! Not that it really matters; there are no Z80 > applications for M100, and the Z80 can't run 8085. > > But, what this means is that having a Z80 processor for CP/M in M100 is > very close to reality. > > And it is kinda neat to see the good old M100 interface work using a Z80 ;) > > Learned a lot along the way for how to modify 8085 code to run on NSC800. > Also the subtle difference in how NSC800 deals with the Timer driven > interrupt TP. > > More to come, Steve > > On Fri, 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. > > > >
