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ATI/AMD 7xxx and PCIe lanes (x8, x16, ...)

Tags:
  • Radeon
  • AMD
  • Crossfire
  • Graphics
Last response: in Graphics & Displays
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June 22, 2011 6:37:14 PM

Hi folks,

I am putting together a gaming rig with 3 monitors (not NVidia 3D), and will be buying two AMD 7xxx cards and CrossFire-ing them, when they come out. In the meantime, I will be using a decent-but-cheap graphics card (Radeon HD 6950).

Since I want my rig to be ready for two AMD 7xxx cards in CrossFire, I was hoping you guys knew how many PCIe lanes I need. For current cards and sub-ludicrous resolutions, it seems using a motherboard with x8/x8 or x16/x8 PCIe lanes is perfectly alright. Do I need x16/x16 lanes for the upcoming AMD 7xxx cards?

Thanks,
Willard.

More about : ati amd 7xxx pcie lanes x16

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June 22, 2011 6:58:54 PM

Since the 7000 series cards aren't out yet, and no specs for them have been released it is really hard to say. Unless the 7000 series offers a rather large boost in GPU power over current video cards, the x8/x8 setup would probably not cause a large bottleneck. On current high end cards, an x8/x8 setup will cause a bottleneck of 3 to 5% at most. Unless the 7000 series cards are much more powerful than current cards, I don't see that bottleneck increasing to the point where it would be significant enough to go for an enthusiast platform simply to get the extra PCIe lanes.
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June 22, 2011 7:24:45 PM

If you can get a 16x/16x board then get one. If you're going to be paying $300+ per GPU there is no reason to make them 5% slower by not paying $30 more for a better motherboard.
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June 22, 2011 7:28:24 PM

If your going AMD I should add that there aren't too many AM3+ boards out yet so you may want to wait till more models are available and reviews are in ^_^. If you're going Intel then it really doesn't make much of a difference. Since the NF200 adds latency there isn't much point in it over the PCI-E controller on Sandybridge is pretty good even with just it's 8x/8x setup.
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June 22, 2011 7:32:34 PM

I'm going to assume the Op edited out the bit about wanting to use Bulldozer as i see no mention of wanting an AM3+ board ?

But i fully agree and im going to be very blunt here, no offense intended but only a complete novice or an idiot if they knew what they were doing would even consider a board that wasn't 16 X 16

Mactronix :) 
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June 22, 2011 8:14:40 PM

Thanks for your replies :-)

Has anyone seen a Z68 chipset motherboard which delivers full x16/x16 lanes? If so, I would really appreciate a link.

Supernova1138 said:
Since the 7000 series cards aren't out yet, and no specs for them have been released it is really hard to say. [...] On current high end cards, an x8/x8 setup will cause a bottleneck of 3 to 5% at most. Unless the 7000 series cards are much more powerful than current cards, I don't see that bottleneck increasing to the point where it would be significant enough to go for an enthusiast platform simply to get the extra PCIe lanes.

megamanx00 said:
If you can get a 16x/16x board then get one. If you're going to be paying $300+ per GPU there is no reason to make them 5% slower by not paying $30 more for a better motherboard.

I wouldn't mind a tiny drop in frame rate, but it would be great to get the full squeeze out of my graphics cards. Since it is better to be safe than sorry, then I will grab a x16/x16 card if I can find one.

megamanx00 said:
If your going AMD [...] If you're going Intel then it really doesn't make much of a difference. Since the NF200 adds latency there isn't much point in it over the PCI-E controller on Sandybridge is pretty good even with just it's 8x/8x setup.

My plan is indeed to "go Intel". I am most interested in the Z68 chipset, and the i5 CPU.

mactronix said:
I'm going to assume the Op edited out the bit about wanting to use Bulldozer as i see no mention of wanting an AM3+ board ?

Nope; I just neglected to mention anything about the build I have in mind. The only editing I did was to fix a few grammar bloopers.

mactronix said:
But i fully agree and im going to be very blunt here, no offense intended but only a complete novice or an idiot if they knew what they were doing would even consider a board that wasn't 16 X 16

You can be as blunt as you want, as long as you are completely factual and honest ;-)

The thing is I have seen several reviews demonstrating that graphics cards today are not utilizing the full bandwidth provided by >8 PCIe lanes. Example: http://www.tomshardware.com/reviews/p67-gaming-3-way-sl... .

Unless I find a motherboard which can deliver full x16/x16 (not x8/x8 to two x16/x16 ports, not x16/x8 to two x16/x16 ports, etc), I think I am going for the Asus Maximus IV GENE-Z motherboard http://www.asus.com/Motherboards/Intel_Socket_1155/Maxi... . It is a microATX card which can house two graphics cards, with at least x8/x8 bandwidth. (I am the kind of ignorant fool that tries all he can to squeeze his build into as tight a space as possible, and then worry about heat generation later).
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June 23, 2011 7:10:07 AM

Best answer selected by willardthor.
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