When I was using my Athlon 1.2, which was unlocked, I was able to run the FSB at 166 without any problems at all. But I had to run at CAS 2.5, everything else on aggressive settings. Both my IDE drive and SCSI drives didn't have any problems as well as all my PCI cards (firwire card, SB Live!, Intel NIC, and Adaptec SCSI 2). I'm currently running 150 because my locked 1700+ maxes out at 1650 Mhz.