What high-end PCI-E 2.0 graphics cards are backwards compatible with PCI-E 1.0?

Question

I know that the PCI-E 2.0 interface is backwards compatible with the PCI-E 1.0 interface. However, I'm wondering what high-end cards (e.g., GTX 400 series or better) will be backward compatible; do any of them require the extra bandwidth of PCI-E 2.0?

An addendum:

If PCI-E 2.0 support is optional, can I expect a GTX 460 1GB to outperform 2 x 8800 GTX 768MB in SLI on PCI-E 1.0? I would lose 512MB in VRAM but gain ~200MHz on the core clock, and more than double the 1800MHz effective memory clock to 3800MHz (not to mention DX11 support).

I feel that I would see a noticeable performance improvement. Is there any way to be sure without buying and benchmarking?

Thanks!

Answer 1

While I haven't seen any test with the latest card the tests I've seen indicated that the PCI 1.0 vs 2.0 only matters if you have a narrow slot (ie 4x instead of 16x) or are using multiple cards for SLI/Crossfire. With a single midrange card like GTX 460 I wouldn't worry as long as you put it in a x16 slot.

Also, your not actually loosing any VRAM. Since it is so slow to access the other cards VRAM they both have to load all resources into their own VRAM. So while in SLI you physically have twice the VRAM you also have to load two copies the resources, one into each VRAM, the end result is the same as if you had had only 768MB of VRAM.

This comparison compares a single 9800GTX to a GTX 460. Not exactly 8800GTX SLI vs a GTX 460, but close enough to draw some conclusions. The 9800 GTX is only slightly faster than the 8800 GTX, and with the assumption of around 70% SLI scaling you can get a picture of what your upgrade would offer. Rough conclusion is that a GTX 460 would be a bit faster than 8800GTX SLI.