Thanks for your help, zlojack.

Later I'll try setting my FSB at 425MHz and TRFC at 60.
Maybe I've been insisting too much on setting TRFC at 50 or 55.
When I try pushing Performance Level too high the system doesn't even boot.
The Transaction Booster setting enabled/disabled depends a lot on the divider being used.
I wish Asus would call it Performance Level or tRD instead...

Thanks again for your post.
Take care