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HD 7870 in crossfire PCI-E performance

Last response: in Graphics & Displays
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January 25, 2013 10:08:57 AM

Hello. I am using two HD 7870 in crossfire, but I have two pci-e slots for graphics cards, one is pci-e 3.0 16x, but the other one is PCI-E 2.0 16x(4x mode). I keep reading on internet that video cards in this kind of setup, decreases video performance. So I understand that having 16x/8x or 8x/8x is better option, but it's still better having two video cards than one HD 7870 in my case, right? Or does one HD 7870 in pci-e 3.0 x16 slot performs better, than two hd 7870?

My specs
Processor: i5-3570k
Mobo: P8Z77-V LX
RAM: 4x4GB HyperX T1 1860MHz
VIDEO: 2x Sapphire HD 7870 GHz Edition
PSU: GS700
January 25, 2013 10:18:24 AM

I've noticed that GPU-Z shows that my cards are connected to PCI-E 3.0 x16 @ 16x and PCI-E 3.0 x16 @ x4, although in my mother board manual it is said that I have 1 PCI-E 3.0 x16 slot and 1 PCI-E 2.0 x16(x4) slot.

January 25, 2013 10:26:48 AM

The two cards will still perform better than one, but would do a little better with x8/x8 slots. There is a review floating around here somewhere showing the difference between slots and basically 3.0 x4 is similar to 2.0 x8. You really aren't losing a ton of performance, maybe 10%. If you want to check performance just do a quick benchmark in a game that has it with crossfire enabled/disabled to see the difference.
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January 25, 2013 12:08:28 PM

I wouldn't Crossfire 7870's.

Crossfire is much more prone to microstutter than SLI and the lower the card in the pecking order, usually the more time spent in the 99% and rendering frames, so it's choppy and less smooth feeling.

Just sayin'.
February 7, 2013 5:35:34 PM

Hey intersectnr7, can i ask you something?

Im looking forward to buy a second 7870 to my pc, but my motherboard does crossfire only at x16/x4, like yours.

So.. could you post some of your games performance here?

It'd be of much help.

Thank you!
February 7, 2013 7:03:17 PM

gguaiato said:
Hey intersectnr7, can i ask you something?

Im looking forward to buy a second 7870 to my pc, but my motherboard does crossfire only at x16/x4, like yours.

So.. could you post some of your games performance here?

It'd be of much help.

Thank you!


Hey gguaiato, in my opion, don't buy second 7870, because it will give you about 10% performance increase. Just week ago, I sold my second 7870. Well, about performance. I was playing AC3, DmC, Dead Space 2 on max settings, and it just gave me 10 fps boost in FRAPS, nothing big. I suggest you to stick with one 7870 or buy different motherboardm, because x16/x4 is not the way to go. Hope this helps, despite my corrupted english lol. :pt1cable: 
!