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Dual 7870's at x8?

Last response: in Overclocking
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January 24, 2013 6:18:01 AM

I have a asRock mobo that will allow me to run two gpu's at x8. My question is... is it worth buying a 2nd HD 7870 and running two?

More about : dual 7870

a b U Graphics card
January 24, 2013 6:51:12 AM

Let me rephrase the question: Will x8 vs x16 lanes make a difference? No.

Is it worth buying a 2nd HD7870 for Crossfire: different topic
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January 24, 2013 7:03:22 AM

abbadon_34 said:
Let me rephrase the question: Will x8 vs x16 lanes make a difference? No.

Is it worth buying a 2nd HD7870 for Crossfire: different topic

I cant run 2 cards at x16, either one at x16 or two at x8.
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a b U Graphics card
January 24, 2013 7:11:22 AM

I understand that. Performance wise it will make no difference, maybe 1 or 2% at most between runnning 2 cards at x16 and running 2 cards at x8. You're board will not be an issue.
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January 24, 2013 7:18:44 AM

Actually there is one key piece of information being left out here.

Running dual 7870's in crossfire on your mobo (that has two pcie 3.0 slots running x16/0 or x8/8) will not likely saturate the channels.

Running the same xfire setup in x8 + x8 2.0 slots may cause issues.

As far as needing a second card, it is entirely dependent on what software you are running at what settings, and what type of performance you are trying to obtain.
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January 24, 2013 7:42:34 AM

welshac said:
Actually there is one key piece of information being left out here.

Running dual 7870's in crossfire on your mobo (that has two pcie 3.0 slots running x16/0 or x8/8) will not likely saturate the channels.

Running the same xfire setup in x8 + x8 2.0 slots may cause issues.

As far as needing a second card, it is entirely dependent on what software you are running at what settings, and what type of performance you are trying to obtain.

My mobo is the asRock z77 extreme4 which has pci-e 3.0.
All i am wanting is to get better frame rates in games, plus also reducing FPS lag when recording game play.
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a b U Graphics card
January 25, 2013 1:38:00 AM

trigg said:

All i am wanting is to get better frame rates in games, plus also reducing FPS lag when recording game play.


You will get high frame rates in games that support it (most), though you may need to address micro-stutting with a program like RadeonPro. As for "FPS lag when recording game play" if you are referring to lower FPS while recording than not recording this may be more an issue with your recording technique (settings and hard drive setup).
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a b U Graphics card
January 25, 2013 4:50:58 AM

First, the micro-stutter issue with multi-gpu setups is greatly exaggerated. It exists by the nature of multi-gpu setups, but if you keep your fps sufficiently high (over 50 in my experience), you won't notice it.

x8/x8 pci-express 3.0 is enough bandwidth for crossfire 7870s. It's the same as x16/x16 pci-express 2.0. I still don't think there are any single-gpu cards out that can fully saturate a x16 pci-express 2.0 lane.

Monitor your CPU and GPU usage before buying new hardware. Your recording lag may not be a GPU issue. It will take a hit, but recording stresses your CPU and hard drive. You always want to record to a separate internal hard drive (may not be an issue with SSDs). Youtube will only take 30fps video, so it's fine to record at 30fps unless you plan on doing slow-mo shots, then record at 60fps (so you can do 1/2 speed shots without losing quality). Recording at a lower framerate will alleviate some performance issues.
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January 25, 2013 8:43:57 PM

hapkido said:
First, the micro-stutter issue with multi-gpu setups is greatly exaggerated. It exists by the nature of multi-gpu setups, but if you keep your fps sufficiently high (over 50 in my experience), you won't notice it.

x8/x8 pci-express 3.0 is enough bandwidth for crossfire 7870s. It's the same as x16/x16 pci-express 2.0. I still don't think there are any single-gpu cards out that can fully saturate a x16 pci-express 2.0 lane.

Monitor your CPU and GPU usage before buying new hardware. Your recording lag may not be a GPU issue. It will take a hit, but recording stresses your CPU and hard drive. You always want to record to a separate internal hard drive (may not be an issue with SSDs). Youtube will only take 30fps video, so it's fine to record at 30fps unless you plan on doing slow-mo shots, then record at 60fps (so you can do 1/2 speed shots without losing quality). Recording at a lower framerate will alleviate some performance issues.

Thanks for the amazing reply! I never knew youttube only took videos at 30 fps... That pretty much fixes my problem because i was trying to record at 60 fps.
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January 25, 2013 8:44:42 PM

Best answer selected by Trigg.
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