Is running Crossfire 8x speed faster than one GPU at 16x speed?

[CGBS]

I'm looking at new AMD motherboards and the 790GX chipset supports crossfire, but with each card running at half speed (8x). The 790FX chipset allows for both cards to run at 16x speed.. I know there will be a difference between the two crossfire setups, but is running two cards at 8x speed faster than running one card at full PCIe x16 speed?

This is mostly curiosity; I don't plan on running a crossfire setup immediately.

[O.G]

I would say the 2 cards would be faster, using the argument that none of your scenarios (8x or 16x) will use anywhere near the available bandwidth.

[Richard Hammond]

2 cards will be faster than 1 but both cards will be running at 95% of max due to 8x bandwidth limitations, it works out at only a few FPS though.

[+PeterUK MVC]

Not really a problem when its PCI-e 2.0

[Richard Hammond]

Not really a problem when its PCI-e 2.0

Wrong, even when its PCI-e 2.0 there is still a performance impact of running crossfire or sli in 8x lanes instead of 16x lanes

Benchmarks

[O.G]

If your option is a GX chipset and 2 cards or an FX chipset and 1 card (seems a budget related choice to me), then the latter is better as you can aways add another card and run both at the full 16x. The former would be a false economy.

[+PeterUK MVC]

Wrong, even when its PCI-e 2.0 there is still a performance impact of running crossfire or sli in 8x lanes instead of 16x lanes

Benchmarks

To me its a small impact this being based on a HD 4850 you'd think high end cards would really have an impact in x8 by x8 but you be surprised.

X58 x16 by x16 vs P55 (really the CPU) x8 by x8 HD 5870 crossfire

http://www.anandtech.com/mb/showdoc.aspx?i=3649&p=1

[svnO.o]

To me its a small impact this being based on a HD 4850 you'd think high end cards would really have an impact in x8 by x8 but you be surprised.

X58 x16 by x16 vs P55 (really the CPU) x8 by x8 HD 5870 crossfire

http://www.anandtech.com/mb/showdoc.aspx?i=3649&p=1

This is good to know. I got 2 4770s in crossfire with just 1 x16 slot and 1 x8 so they both run at x8. Was too lazy to research it myself.

[+shift. MVC]

Only issues I've found which there are actual numbers for are for the 5970.

http://www.hardwarecanucks.com/forum/hardw...-review-22.html

[Argote]

As others have said, this will NOT be an issue unless you're going for very very powerful cards.

So go for 2 cards.