Ok so my Sapphire 512mb 2900 pro turned up a couple of days ago, and it turned out to be a 256bit version! Sapphire don't even list a 256bit version on their website!!

Even worse - can't get it stable past 755Mhz on the core (mem OCs to a respectable 1080Mhz though).

Rivatuner says that the vGpu is 1.08v so perhaps this is limiting the core OC. Is there a bios version that I can use to raise this? It stays under 70'C at load so I assume there's enough headroom to play with there.