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Will PCI-Express x16 slot (running at x8) handle a graphic card?

Last response: in Graphics & Displays
December 10, 2008 3:52:37 PM

Hey, quick question!

I noticed with the gigabyte motherboard I'm thinking of getting - GA-EP45-UD3P that it has two PCI Express x16 slots. But upon closer inspection of the specs, I see this:

1. 1 x PCI Express x16 slot, running at x16
2. 1 x PCI Express x16 slot, running at x8
(The PCIEx16 and PCIEx8 slots support ATI CrossFireX technology and conform to PCI Express 2.0 standard.)
3. 3 x PCI Express x1 slot
4. 2 x PCI slots

Does that mean I can put two graphic cards that utilize the x16 slot on this motherboard? For example, can I put two Radeon 4850 on this motherboard but one will be throttled?

December 10, 2008 4:56:21 PM

ok i had a mobo that did the same thing the 650i sli, what it means is yes you can run crossfire but the link speed will be at 8x/8x not 16x/16x. but dont fret my friend running at 8x/8x doesnt have any noticeable performance difference(s). heres how it ranks in performance, if you have a pci-e slot at 16x then its 100% speed but lower it to 8x then it runs at 95% speed. i had a link that compared 8x/8x sli versus 16x/16x and the difference was 1-3 fps so you good with that mobo. i wish i had the link for the comparison i had. if i find anything ill post it.
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December 12, 2008 4:39:03 AM

xxcoop42xx said:
heres a crossfire hd4850 8x/8x vs 16x/16x comparison.

heres for sli 8x/8x vs 16x/16x (the 750i sli runs sli at 8x/8x)

Can't comment on the sli article, but the Tweaktown article on Crossfire has been pretty heavily discussed on various forums and many other sites don't quite find the same results, including this very site!

PCI Express & CrossFire: Scaling Explored

Over all the games and settings, the differences they found between a P45 (running 8x/8x) and a X48 (running 16x/16x) was about 4%. That's using two HD4870's, which should be more crippled by lack of bandwidth.

I have the same board you're looking at, and a pair of HD4850's in Crossfire. I get great results in the games I've tried so far on the highest settings. I don't think you have anything to worry about with 2 4850's.




"The X48 was also roughly 6% faster than the P45 chipset, and I would suggest that this is a best case scenario for the high-end X48 chipset."

6% measured by This translates into a few extra FPS at best.

$120 for a few extra FPS? Doesn't seem worth it to me...
December 12, 2008 5:02:36 AM

actually (i didnt click on the link) but if its a evga 750i it runs them at x16/x16... love evga :) 
a b U Graphics card
a b V Motherboard
April 9, 2010 10:06:10 AM

do we have pci express x8 slot
a c 84 U Graphics card
a b V Motherboard
April 9, 2010 10:41:53 AM

yey necrothread with nonsense comment... or is that a question?? :/