I just bought a chess computer with a 65c02 inside and it goes at 5 Mhz (4.9152). Can i overclock it to 10 mhz?

regards
Ricardo

You probably can't go double. What's the speed of the memory and glue logic on it? That might be more of a limiting factor than the processor itself. How fast are the processor and peripheral ICs marked for? The best thing to do would be to give it a variable-frequency clock source and see how fast you can take it before it starts having problems (probably meaning crashing), then back it off 20-25% for a safety margin so it will keep going reliably when the temperature is higher or the power supply voltage sags a little.

I made such a variable-frequency oscillator (VFO) with a 74HC14 for this purpose, and found my workbench computer with 4MHz parts started having problems at just a hair over 7MHz, so I run it at 5MHz. I just made another tiny VFO using a 74AC14 on a perfboard with two planes (one for +5V and one for ground) for the next computer which I hope will do around 20MHz. This VFO tops out at 73MHz, which, after the flip-flop dividing by 2 for symetry, results in 36MHz max.

The basic idea is to just put a trimmer resistor from output to input of one of the Schmitt-trigger inverters, and a small capacitance from the input to ground. Buffer the output with another inverter section. For maximum frequency, just use the input capacitance itself on the first inverter. Otherwise, have jumper or DIP switch selections for 10pF, 22pF, 47pF, 100pF, etc. to ground. (You can take it further for lower frequencies if desired.) My trimmer on the second VFO is 20K, and I put a 330Ω resistor at one end to limit it. You can still see 73MHz on my 20MHz oscilloscope, but it's small and looks almost like a sine wave. My 512MHz frequency counter confirms the frequency.

Thanks GARTHWILSON for your fast answer, the computer is on my way home and it will take maybe 10 to 12 business days but i will check all you are asking for once i have it (ram,rom,peripheral IC). Then i will make the test with a VFO.

regards
Ricardo

can you please post name/brand?
tnx

mephisto polgar

ricardo