Update. I have refined my NSC800 aka Z80 conversion for M100 somewhat. I now have a very simple adapter board that converts the 80c85 socket to accept NSC800. Small and simple. Plug and play.
The main rom needs to change to a patched version that I have. To do so, you need to use one of the various means to convert the strange M100 main rom socket to something more standard. Why? Well I am still pushing towards a nice Z80 solution for CP/M. Besides.. the solution is so clean it is really cool. Hard to resist! The M100 could have easily been designed with this processor to begin with. So why not ;) My thinking is to offer this as a simple kit or maybe even just release the board. The BOM is really small. Processor is easy to get off ebay. One thing that would be nice, is a new version of tsdos that avoids all the special 80c85 opcodes....compatible with 8080. Then it could run on z80 as well. Even a patched teeny would be fine I suppose. On Thursday, July 11, 2019, Stephen Adolph <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. > > > >
