Well, the problem was that Marco's jumper setting for 600 mhz was actually
for 533. I found another post with more settings.
snip
Earlier in the year Jeff DeMaagd posted a list of settings as follows
If it were this year, I think someone else posted it. :) I did write
the original text, I think it was around 1998 or 1999 that I posted it.
I still have the same machine. It was a 500 that ran 566 pretty
decently for a while, oddly enough it wouldn't run 533 at all. I quit
overclocking it a few months later when it suddenly wouldn't boot. It
was a machine that I needed to run stably so overclocking made little sense.