I don't know
anyone else that does that around here
If you were using the 1/5 PCI divider, then your IDE interface wasn't being pushed as hard as you are at 166 and 1/4 (40 vs 41.5). Won't the IWill allow you to use the 1/4 divider above 166?
And HTH is the PCI divider affecting your memory bandwidth? (especially since your core speed was about the same)
* wonders about the IWill board * :shrug: