I bought one of those so called 'pretested' Celeron 566 FCPGA which the seller claimed it can run at 850/100, but I can't get that speed at my system. I tried to yank up the v-core to 1.8v and still no go. I can only clock it at 708/83, and that runs fine at 1.5v v-core. What gives? Anyone else have same experience? Help please.

Will a better HSF help?

If it matters at all, here's the list of all my hardware.
Hardware:
C566 FCPGA
Asus CUBX
Enlight 7237
Micron 128 Cas2 SDRAM
Golden Orb
WD Expert 7200rpm 20 Gig
All PCI cards run fine at 41 Mhz PCI bus speed
Soundblaster AWE 64 ISA