Most of us with 450s can barely reach 500MHz, let alone do it on a 350. You would be quite lucky to reach 450MHz, but most probable for you is 400MHz or somewhere around there. The AMD K6X series, in it's current form, is not designed to run at speeds of 500MHz. Unless you got a really good chip, you are going to have to wait until AMD releases the .18u and copper-based K6-IIIs before you can hit 500MHz and beyond.
Try it at 450 and if you can reach that, be happy.
-JGene
[This message has been edited by JGene (edited 08-16-99).]