yah good point. not really sure about all the impacts of 5MHz. I'm guessing it will need some patches in certain things. The capability is a soft switch meaning you can just type a simple OUT command and switch on the fly to fast mode. So, perhaps that's the work around. Might really mess up system time though. It's an experiment. 5MHz is one option; it can be ignored. In fact if you are good enough at soldering, you can re-use the original 80C85, and simply use it as a switcher.
A long time ago I bought some 8MHz Tundra 80C85 parts. This board finally gives me the opportunity to play around with them. On Thu, Jul 11, 2019 at 10:38 AM Kurt McCullum <[email protected]> wrote: > Steve, > > Not owning a 100 I can't dive into this but I am definitely watching to > see what you come up with. The 5mhz upgrade is really interesting. I do > wonder what that will do to all the apps that have specific timing (ie: > TS-DOS delay). Will the clock get messed up? > > But if this leads to CP/M then the existing ROM and applications don't > really matter. > > Kurt > > On Thu, Jul 11, 2019, at 7:31 AM, Stephen Adolph 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. > > > > >
