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GTX 670 is running at pci-e x8 , not x16 because of dedicated physX

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December 14, 2012 10:41:11 PM

I just noticed something today when I was looking at some GPU-Z specs and whatnot, and I noticed that since I'm using a GTX 460 for dedicated PhysX along with my 670, the PCI-E slot the 670 is in is running at x8 bandwidth, not x16 if it was alone.

Is this causing bottlenecking my video card? Will I get significantly better performance if I remove the 460 and let the 670 do it's own thing? My mobo is a Gigabyte GA-P67A-UD4-B3 with an i5 2500K

thanks for the response!
December 15, 2012 2:46:07 AM

No it's not creating a bottleneck. PCIe 3 x8 is about equal to PCIe 2 x16, more or less. Tom's did a review on PCIe 3 around the time it released. If I recall, you don't even gain a full frame most of the time, the current technology just isn't needing it.

Will you see a performance increase taking out the 460, to run in x16? Maybe a frame, usually half a frame, if there is actually a gain. You're much better off using the 460 for PhysX as you are. It's just the limitation of Z77/68, where multi-GPU setups can only be run in x8/x8.

I'd link you the article, but multitasking on Android isn't my strong suit >.<
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a b U Graphics card
December 15, 2012 3:12:41 AM

Gpu set up look like this. 1x gpu=x16; 2x gpu=x16+x16=(x32); 3x gpu=x16+x8+x8=(x32); 4x gpu=x16+x8+x4+x4=(x32). so 2xgpu=4xgpu. Solution: put that 2 gpus in x16 u get x32.
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a b U Graphics card
December 15, 2012 3:15:57 AM

U can get full advantage(100%) of gpu in x16 slot. in x8 slot u get only (50%) speed.
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December 15, 2012 3:20:59 AM

If I do recall, using Physx with a too-weak GPU can actually reduce the frame-rates than running it on the main powerful GPU or letting the CPU do the physics/etc work.
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a b U Graphics card
December 15, 2012 3:43:13 AM

Using a separate weak Physx card can be slower than using a single strong card.

The GTX460 is powrful enough for Physx in all games.
And you wont gain anything by using the full PCIE3.0 -x16 slot for the GTX670. It is fast enough @x8.

That said, IMO Physx is over rated bullsh!t.
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December 15, 2012 3:50:40 PM

hytecgowthaman said:
Gpu set up look like this. 1x gpu=x16; 2x gpu=x16+x16=(x32); 3x gpu=x16+x8+x8=(x32); 4x gpu=x16+x8+x4+x4=(x32). so 2xgpu=4xgpu. Solution: put that 2 gpus in x16 u get x32.

Z68/77 is going to force it in x8/x8 regardless. Just the limitation it has.

The 460 for PhysX I would imagine is capable. The most advanced game with it I can recall is Borderlands 2, which should be fine for a 460 Physx only. Personally I'd probably test it and see, not like it's hard since the you can just toggle where the PhysX is worked out.
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