update for the hardware geeks (I may be the only one?) The first bottleneck is the data bus. Swapping M2 for a faster 74LS245 yields *5MHz.* Of course this is bad for current, so maybe there is a better CMOS part out there. continued tweaking...
On Thu, Oct 29, 2020 at 12:52 PM Stephen Adolph <[email protected]> wrote: > I have an early result on overclocking the M100. > > In my testbed I have a stock M100, with a couple of changes. > 1) I have a socket on the 80C85 > 2) the standard 2.45MHz clock is generated and fed to the system so that > stays constant > 3) I feed the CPU with a separate clock that can range from 2.5 to 8 MHz. > 4) to overclock I use the Tundra 80C85 rated at 8 MHz. > > Initial results: > The following clock rates worked stably: > 2.47 MHz > 2.74 MHz > 3.09 MHz > 3..53 MHz > 4.11 MHz > > The M100 abruptly dies at 4.94 MHz. > > So at 4.11 MHz, the serial port worked fine. The only difference other > than general speed, was that the audio tones were higher. > > I thought it would be faster to be honest. So maybe it is the 81C55. I > happen to have a 5MHz rated device, lets try that. > > Answer = no. A 5MHz 81C55 does not improve things. So, it might be the > RAM or ROM that is too slow, or who knows. > > Anyhow that seems to be the low hanging fruit. 4MHz. > There are 80C85 out there that are rated at 5MHz, and the NSC800 can be > had at 4MHz. > > ...Steve > > > > >
