GhoXen

Recently I've bought a HD5870, and I plan on using my old 8800GTS640MB with it for physx.

My motherboard is Asus M4A79XTD EVO, which seems to have 2xPCIe 2.0 x16, but its Crossfire mode is only x8/x8 instead of x16/x16. A friend suggested that if I plan on using 8800GTS as the physx card, I should try get my crossfire mode into x16/x4 with BIOS. Is that a good idea and is that possible with my motherboard?

I've also read somewhere in the main thread about nvidia blocking physx to ati cards that with a HD5870 on x8 I'd only lose about 2% performance? That sounded too good to be true.

Thanks in advance!

My full system specs in case additional information is needed:
AMD Phenom II x4 965
MSI HD5870
2x2GB DDR3 memory
M4A79XTD EVO motherboard
WD 1TB HDD

Summary Version:
1. By having HD5870 and 8800GTS together with x8 dual link, will I expect performance loss compared to single HD5870 x16?
2. Is it possible to modify the crossfire mode of x8/x8 into x16/x4 with my motherboard(Asus M4A79XTD EVO)?

shivansps

Ive see in some mbs the option to those the bandwitch of the PCI-E ports, but i never see this option on an AMD mb.

What about "taping" the lanes of the 8800GTS card allowing only x4 lanes?

The MB maybe re-assign those lanes to the 5870.

http://www.tomshardware.com/reviews/...ing,927-4.html

The second image.

darthcyclonis

I would not be to concerned. Remember PCIE 2.0 @ 8X is the same bandwidth as PCE 1.1 @ X16. I can assure you that since the 5870 it is not crossfired will not be using all the bandwidth. If there is a loss it is probably less than 2 to 1% tops.

PUTALE

I do not think that any card will saturate the pcie too much. I think only the dual gpu cards will stress it a bit but other than that, any single card only get about a few percent diff that is hardly detectable in real world.