Crossfire (16x & 4x)

[xboxist]

Guys, I need help understanding what I'm dealing with here. I have the board in my signature, and a 5770. I have access to another 5770 for virtually pennies, but my board's manual says something odd about the slots:

(1) PCI-e x16
(1) PCI-e x16 (running at x4)

Does Crossfire use the slowest bus used in the setup, and thus means I'll basically be running Crossfire at x4? Even so, would that ultimately be worse than a single 5770 running at x16?

Thanks for any insight on this.

 

[thilanliyan]

I don't think it will be slower than 1 card because I don't believe a 5770 saturates the PCI-e x16 slot.

 

[cusideabelincoln]

No it won't slow down the other slot, and you will see a performance boost.

 

[xboxist]

Well that's good that it shouldn't make things any slower... but should I even bother trying it? No point really unless it results in noticeable gains.

edit: thank you, cusideabelincoln.

 

[Termie]

Take a look at this article on PCIe slot scaling: http://www.tomshardware.com/reviews/p55-pci-express-scaling,2517.html

You should be ok - it will be faster than one card, but your cards will run slower than they would in x8/x8 or x16/x16. If it's truly costing you "pennies," it's probably worth the trouble just to check it out, but don't expect to double your FPS.