I see 2 reasonable options. Wondering what interest there would be / reactions to these 2 options.
Option 1. 80C85/4MHz. 1.66x speed increase - supports classic M100 use and CP/M - compatible with stock CPU, stock RAM, stock Main ROM, and existing option ROMs - CPU adapter board with 8MHz crystal - (must remove 80C85 and install socket) Option 2. 80C85/5MHz 2.0x speed increase (approach also works for 6MHz) - supports classic M100 use and CP/M - compatible with stock CPU (or any 80C85 so it seems) - CPU adapter board with 9.8304 MHz crystal - main ROM adapter board + fast 27C256 EEPROM - use with REXCPM for fast main RAM + option ROMs - (must remove 80C85 and install socket) On Sun, Nov 1, 2020 at 6:44 AM Stephen Adolph <[email protected]> wrote: > Final story on 8MHz (well final for now!). > > Actually, the processor/ram/keyboard all work at 8MHz. Only one thing I > can see, and it is pretty important, doesn't. The LCD. > The driver chips have to communicate with the CPU, and they are just too > slow to get their data on the bus in time. > So, I think that's the end of the story; no clear way to improve on the > Driver response time. > > 6.144MHz is exactly 2.5x nominal clock rate. That seems to be achievable. > > > On Sat, Oct 31, 2020 at 7:12 PM Stephen Adolph <[email protected]> > wrote: > >> On Sat, Oct 31, 2020 at 5:52 PM Joe Grubbs <[email protected]> wrote: >> >>> Aww yeah! I'm liking where this is going. Will the sluggish original ROM >>> handle 8Mhz+? >>> >> >> No, for sure not. Right now I have a 120nsec EEPROM in the socket and it >> supports 6.2 MHz. >> If I simply place the original ROM back in - no go. >> But the Main ROM is the easiest thing to replace. It is already >> socketed! There are many ways to address it. >> >> So far here are the changes to run 6.2 MHz (my current setup) >> 1) you need a faster CPU + crystal. I'm making a board for that. Which >> CPU - TBD. There are a few choices. (I really should try the stock CPU >> and see how fast it really is. I am currently using the 8MHz Tundra 80C85 >> CPU) >> 2) you need faster RAM. You could use REXCPM to solve that problem. >> Otherwise... a lot of soldering work! >> 3) faster main ROM. Teeprom would be a good solution here. >> 4) improved M2. stock = TC40H245 (good to 5MHz). I have piggybacked >> 74HC245 (6MHz) >> >> I'm puzzled by what is failing to work at 8.2 MHz. Everything so far >> looks ok. I'll keep poking around.... >> >> >> >> >>>
