Do you know if it switches from 1/4 to 1/5 at 166 or 167? I can't remember if you said it switches when the PCI bus is equal to or greater than 41.5 Mhz. I'm guessing its 1/5 at 166 because I've been running 166 x 8.5 = 1411 for a few days now without any drive problems. I think my WD 20 gig 7200 rpm probably would have problems before 41.5 Mhz.