I am running mu L6-II 350 at 400 for about a couple of months and dont have any problem. I havent changes anything other than the multiplier, not even the voltage - its still 2.2V! It may run quite well, at 427 MHz with a bus speed of 95 MHz, if cooled well. Mine wasnt so it dint boot through.
A 50 MHz OC is quite okay for most K6-IIs, one of my 400s dint work ay 450 though. Another did! Might need higher voltage to go higher, but 2.8 from 2.2V is pretty much high.
girish
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