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PCIe bus overclocking for SLI/Crossfire: still dangerous? Or just irrelevant?

post #1 of 10
Thread Starter 
I came across a youtube video where a guy tested a 980Ti SLI setup on PCIe 3.0 at 8x/8x and 16x/16x and saw noticeable differences in min/avg. FPS in Witcher 3 as well as differences in avg. FPS in other games:

https://www.youtube.com/watch?v=8KOTiee5RqA

So I'm curious, would overclocking a PCIe 3.0 bus in an 8x/8x case make any diff.? Or would it be too small to be noticeable?

Are SATA controllers still affected by PCIe bus overclocks (i.e. data corruption)? What about video cards, can they be fried by excessively high PCIe bus speeds?
post #2 of 10
Tried it awhile ago on my 5820K with 980ti sli since im running 8X/8X.
any higher then .2mhz and USB 3 ports stopped working and threw a error in windows device manager so gave up trying.
post #3 of 10
Quote:
Originally Posted by bmgjet View Post

Tried it awhile ago on my 5820K with 980ti sli since im running 8X/8X.
any higher then .2mhz and USB 3 ports stopped working and threw a error in windows device manager so gave up trying.

I wonder why you run 8x/8x when you can run 16x/8x ?
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post #4 of 10
Quote:
Originally Posted by HeadlessKnight View Post

I wonder why you run 8x/8x when you can run 16x/8x ?

NVe SSD's
post #5 of 10
Quote:
Originally Posted by HeadlessKnight View Post

I wonder why you run 8x/8x when you can run 16x/8x ?

when the card is not actually limited by a PCI-e 2.0 at 8x, does it really matter?

I too, would use an NVMe at full potential over a GPU. When I first got my Samsung 950 Pro I turned the r9 390 down to 8x PCI-e 3.0 and noticed NO DIFFERENCE. Steve at Gamers Nexus also explained that it is less than .5% performance hit running a modern GPU at 8x or 16x.

I would rather have a mega fast booting SSD than an irrelevant number that isnt even fully utilized yet.

http://www.tested.com/tech/457440-theoretical-vs-actual-bandwidth-pci-express-and-thunderbolt/

Memory transfer rates on GPU's these days are sky high..like 11ghz! anyways, your CPU to PCI-e bus cant even keep up with that, hell, even the proposed PCI-e 4.0 cant!
Edited by stephenn82 - 4/14/17 at 8:46pm
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post #6 of 10
your performance differences will be determined by your hardware. if you are saturating the pci-e 3.0 bus at stock speed, you may see performance reductions. Pci-3 seems to downgrade itself to ver. 2 around 107 mhz and pci-e 1 at 125. some systems wont post with even a 103 mhz pci-e bus.

if you can deal with approx. pcie 2 speeds, you may be able to overclock to 125 mhz pci-e, and see gains in vram access. i run mine at 135, and i dont really notice the difference, but my monitor caps everything to 60 fps.

the only way to kinw is to try it out
post #7 of 10
Quote:
Originally Posted by acheleg View Post

your performance differences will be determined by your hardware. if you are saturating the pci-e 3.0 bus at stock speed, you may see performance reductions. Pci-3 seems to downgrade itself to ver. 2 around 107 mhz and pci-e 1 at 125. some systems wont post with even a 103 mhz pci-e bus.

if you can deal with approx. pcie 2 speeds, you may be able to overclock to 125 mhz pci-e, and see gains in vram access. i run mine at 135, and i dont really notice the difference, but my monitor caps everything to 60 fps.

the only way to kinw is to try it out

What if you are using pcie 2 especially in crossfire on an all AMD setup? One dude on this board said he overclocks his AMD setup and sees benefits, I never did it cos of the threat/fear of data corruption
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post #8 of 10
Thread Starter 
Quote:
Originally Posted by stephenn82 View Post

when the card is not actually limited by a PCI-e 2.0 at 8x, does it really matter?

I too, would use an NVMe at full potential over a GPU. When I first got my Samsung 950 Pro I turned the r9 390 down to 8x PCI-e 3.0 and noticed NO DIFFERENCE. Steve at Gamers Nexus also explained that it is less than .5% performance hit running a modern GPU at 8x or 16x.

I would rather have a mega fast booting SSD than an irrelevant number that isnt even fully utilized yet.

http://www.tested.com/tech/457440-theoretical-vs-actual-bandwidth-pci-express-and-thunderbolt/

Memory transfer rates on GPU's these days are sky high..like 11ghz! anyways, your CPU to PCI-e bus cant even keep up with that, hell, even the proposed PCI-e 4.0 cant!

Your article is out-of-date. There are modern games that will show significant losses in perf. w/modern GPU's in SLI when used in a PCIe 3.0 8x/8x setup as opposed to 16x/16x.
post #9 of 10
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post #10 of 10
hard drive data corruption must be chipset-dependant. i had an asrock fm2+ mobo that couldnt boot past 103mhz pci-e bus, but my current asrock Am2+ overclocks the pci-e to 135mhz fine
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