PCI Bottleneck CF

Hi, I was wonding if anyone would be able to give me some more information on PCI scaling when CF. I have one 5770 and are thinking of adding a second however my second PCI x16 is only 4 lanes. How will this effect the performance?

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  1. 4x will hurt your fps but 8x there is very very little penalty. I am guessing that you are using a Intel 9xx based board like a 965 right? If so you might as well try to land a cheap p35 or better board while they are still cheap for better scaling 8x8 vs 16x4 crossfire. Plus you will be able to nuke the cpu more. If it is a AMD based box then I suggest that you do the same while they are still cheap since prices are rising again.
  2. thanks for the reply i have a Asus M4A77TD Pro. I'm not keen to upgrade my mobo seeing i have windows OEM. I've seen the PCI scaling on toms hardware. I thinking the 4x wouldnt hurt as much with a 5770?
  3. OH AM3, since it is pci-e 2.0 it won't be as bad but there will be a bottleneck but not as bad as the older spec so it is worth a shot. It won't scale as well as every one else but 20-40% boost isn't bad plus you can use more monitors if that gets your fancy.
  4. Yes i agree with sbinney. You might see a decrease in FPS if you ran them in crossfire. If i remeber right they run as your slowest card. Which in turn would be the card that is hooked up to the x4. Assuming you use the same cards 5770x2 what you would get is they both would run x4 which would make x8 total. As apposed to your 1 card that runs x16 already. So all in all it would be a performance loss. I would also double check ati's website on if you can actually run it in x4. Most video cards are x8+.
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