Now the 1/5 PCI divider might kick in automatically @ 166, BUT unless you set your mem speed at 266 before you try booting that, your mem will probably prevent a boot, because at 166 on the FSB you'll be trying to run the RAM at 208x2 which needs serious tuning to work up to usually. As far as I can work out, the 266/333 setting is really 2x or 2.5x of the FSB for the RAM. So when you get the FSB way up there you need to drop the RAM multiplier.
I think,
Road Warrior