I'm not trying to steal your thunder (BTW. congratulations for finally getting things running well) or tread on any toes but...
As I had stated in your earlier thread (re. SLi), the GTX 295 is a two GPU solution in a single package with the GPU's bridged and SLI takes place internally. The bridge connects between the the two PCB's that each house one GPU and the signal is transmitted via a single PCI-E x16 expansion slot. In a traditional SLi system, the only way for the two separate cards to "communicate" would be via the bridge (connecting the SLi "fingers") and the PCI-E slots (you can run SLi without the bridge albeit not quite as well). To get the boards to "talk" via the PCI-E slots, you needed a SLi compatible boards - simple. The GTX 295 removes this limitation by presenting a single interface to the motherboard's PCI-E slot and doing all the geek SLi work internally on the card. Of course, if you want two of these powerhouses in your computer for Quad-SLi, you'll need a SLi compatible motherboard. (nVidia has recently unveiled a single PCB version of the GTX 295. The big difference between the old and new model is that instead of using two GPUs on two PCBs, this new card has the two GPUs placed on a single PCB thus lowering overall production costs. In truth, the only possible reason to bother updating the 295 as clocks, thermal characteristics, power consumption etc. are identical to the older model.)
All this means is that having a SLi capable motherboard or not shouldn't matter a single bit in a dual-GPU/SLi solution (eg. 9800GX2 or GTX 295). There are many users on Guru3D with a non-SLi board (nee. CrossFire compatible boards P41, P45, X48 etc.) who happily run GTX 295's without the problems you experienced. You also stated that your first Zotec card was faulty... might this have contributed to your problem? Updating your non-SLi BIOS for a SLi BIOS is very hit or miss, it worked for some but not others. With your single card, you wouldn't know if the SLi portion of the motherboard's BIOS is working or not unless you chuck in a couple of identical cards and try it out.
Blaise
