Not sure how I missed this original post last year, but wow I'm impressed. Please keep at it and keep us updated. This sounds like a very cool venture
________________________________ From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Stephen Adolph <twospru...@gmail.com> Sent: Saturday, May 30, 2020 3:55 PM To: m...@bitchin100.com <m...@bitchin100.com> Subject: Re: [M100] dual CPU project No, it is a plug in board.... but it plugs into the CPU socket (ah....which does not exist!) On my bench system I did the work to take out the CPU and added a socket. Then I plug an expansion card into it. Good idea though about the system bus, I'll have to think about that. I'm almost done a full patch to the M100 Main ROM which makes it 8080/Z80 compatible. In this case I should be able to switch to running Z80 in M100 mode too! Steve On Sat, May 30, 2020 at 2:57 PM Ken Pettit <petti...@gmail.com<mailto:petti...@gmail.com>> wrote: Hey Steve, Oh great! One more emulation I need to add to VirtualT! ;) Nice work! How do you wire it it? System bus? Ken On 5/30/20 5:04 AM, Stephen Adolph wrote: ...and I just now this second got the NSC800 to run in the M100 successfully. It is driving the LCD at the moment. I think the interrupts are different, and more work to do, but it is officially alive. yay! On Sat, May 30, 2020 at 6:32 AM William stewart <wstewart2...@yahoo.com<mailto:wstewart2...@yahoo.com>> wrote: Stephen, Are you suggesting a swap of the 8085? Sent from my iPhone On May 29, 2020, at 7:46 AM, Stephen Adolph <twospru...@gmail.com<mailto:twospru...@gmail.com>> 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 <twospru...@gmail.com<mailto:twospru...@gmail.com>> 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.
