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Crossfire. second card bottleneck?

post #1 of 8
Thread Starter 
My motherboard MSI 870-G45 http://www.msi.com/product/mb/870-G45.html#?div=Detail shows that I have 2 PCIE 2.0 slots (x16 x4).
But when i Crossfire 5770s in this board. The second card does not show PCIE 2.0 as shown in the picture.
au2.png7kp.png

I have run Crysis benchmarks and I have taken the average fps:
resolution: 1440x900
single 5770 1gb pciex16 32.855
single 5770 512mb pciex16 32.715
5770 1gb pciex4 17.1175
5770 crossfire 39.18
5770 cf disabled(1gb on the x16slot) 28.86

So the question is:

1.) Is my PCIE slot x4 not PCIE 2.0 even if MSI tells it is 2.0?
2.) Does crossfiring these cards really help because in my experience, I cannot really tell that I am benefiting in my crossfire?
3.) Assuming that my second PCIE slot (x4) is not pcie 2.0 , do you think this is the cause why I cannot see an increase in performance?

I'll appreciate all the replies as it can really help me address my problems.
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post #2 of 8
I'm not sure why that's happening to you. x16/x4 crossfire isn't going to deter the crossfire setup for your 5770's. They happen to scale very well. If you don't think it's helping you, then disable crossfire and just use 1 gpu on a benchmark like 3DMark and then do it with crossfire enabled. I'm sure you'll see a HUGE difference.

Edit: at the resolution you are running at, you will see little to no difference. sorry, didn't read your benches.
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post #3 of 8
Try switching your video cards, maybe go into your BIOS and see if you can alter the bus speed for your second PCI-E slot.
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post #4 of 8
Thread Starter 
@That Guy So that means I should upgrade to a 1080p monitor?
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post #5 of 8
Quote:
Originally Posted by johnwendel20;13683920 
@That Guy So that means I should upgrade to a 1080p monitor?

Yes. Also grab a cheap bulldozer when they come out smile.gif
post #6 of 8
x4 incurs a 25% hit in scaling, but that... hey you have 2 different memory sized cards?

single 5770 1gb pciex16 32.855
single 5770 512mb pciex16 32.715
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post #7 of 8
Thread Starter 
Quote:
Originally Posted by tsm106;13683988 
x4 incurs a 25% hit in scaling, but that... hey you have 2 different memory sized cards?

Yes. At first I have the 512mb then got the 1gb. I don't understand why gpuz reports my second card runs at pcie x4 and not pcie 2.0 x4 contrary to what the MSI website shows.
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post #8 of 8
You shouldn't cfx a 512mb card with the 1gb card, you end up with jst 512mb effective ram overall in cfx.
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