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
