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Is there really much of a difference?

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April 12, 2010 8:27:36 AM

Hey guys, I have a Giga-Byte GA-P55A-UD4P motherboard and one ATI Radeon HD 5770 graphics card right now. I'd like to go crossfire when I have a little more money in my pocket, but I'm hesitant because the UD4P motherboard only has one PCI 2.0 x16 slot. The other slot is a x8. I've been doing a lot of reading on this I see there's a "bandwith loss" or "bottleneck" when you stick the HD 5770 in a x8 slot. But then I saw in a couple forums people say there's virtually no noticeable difference in performance if the card isn't super high end (i.e. 5870 or something like that). I was just wondering if you guys saw any reviews or tests that could help me determine if crossfire is something I should go for. Any advice is good!

Thanks.

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a b V Motherboard
April 12, 2010 9:31:12 AM

Don't worry at all, a card like the HD 5770 will not be affected by the bandwidth of a PCI-e 8x lane. Yes, there may be like a <1% performance difference, but I doubt it'll be noticeable.

Tom's own article on P55 vs X58 PCI-e scaling, i.e. 8x/8x vs 16x/16x.

http://www.tomshardware.com/reviews/p55-pci-express-sca...

The difference of <10FPS will be even smaller when you use a card which does not require all the bandwidth, like your HD 5770.
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a b V Motherboard
April 12, 2010 10:56:33 AM

claykirk13 said:
Hey guys, I have a Giga-Byte GA-P55A-UD4P motherboard and one ATI Radeon HD 5770 graphics card right now. I'd like to go crossfire when I have a little more money in my pocket, but I'm hesitant because the UD4P motherboard only has one PCI 2.0 x16 slot. The other slot is a x8. I've been doing a lot of reading on this I see there's a "bandwith loss" or "bottleneck" when you stick the HD 5770 in a x8 slot. But then I saw in a couple forums people say there's virtually no noticeable difference in performance if the card isn't super high end (i.e. 5870 or something like that). I was just wondering if you guys saw any reviews or tests that could help me determine if crossfire is something I should go for. Any advice is good!

Thanks.

I can not find a single article that shows HD5770 performance in Crossfire on x8x8 vs x16x16.
I found article comparing X58 (have x16x15) vs P55 (have x8x8) with Crossfire 5850's and indeed the performance difference are small. For HD5770 it will even be smaller being less powerful than the HD5850.
http://www.anandtech.com/show/2847/4

In any case, since you already have the motherboard and one 5770, your most cost effective upgrade path for more powerful graphics for your PC is to get a 2nd HD5770 and do crossfire. Buying another motherboard with x16x16 slots or a single HD5850 will be more expensive options although possible assuming you can sell your excess parts. But If I were you, I'll just go ahead with the Crossfire HD5770.
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a c 295 V Motherboard
April 12, 2010 1:34:57 PM

Hi newcomer and welcome to the Tom's hardware forum.

You won't see a big difference, in fact, the difference between x16 and x8 are 1 or 2 fps.
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April 12, 2010 3:37:17 PM

Like saint said, there are barely any noticeable differences, and even when there is, it barely makes it pass 4 fps...
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April 12, 2010 8:34:15 PM

Thanks a lot guys. I am DEFINITELY going SLI then when I get the cash!! Argh, I love Tom's Hardware :D 
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April 12, 2010 8:38:30 PM

Best answer selected by claykirk13.
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