GPU on 8x lanes

[Genesis730]

I'm looking at getting the ROG Crosshair VII Hero (w/ Ryzen 7 2700x) and running RAID using the two PCIe 3.0 x4 M.2 slots.

It's my understanding that the GPU runs 8x, 4x, 4x lanes and the last 4x will go to the M.2 if used, leaving the GPU at x12 lanes (Which it will only use 8x lanes)

I'm using a GTX 1080ti to run 3 monitors. 2 of them at 1080 and the 3rd at 4k. Is there any concern of performance or bottlenecking at 8x lanes in the scenario?

[dfsdfgfkjsefoiqzemnd]

Nope, you'll need a Titan V before even noticing anything close to a bottleneck on x8. 

 

I ran my own 1080Ti in an x8 slot all winter (was mining on the old 1070 and wanted that one higher up in the case to prevent it from heating up the 1080Ti) and didn't notice any slowdown over x16.  That's with a pair of 1440p 165Hz monitors, no 4K here.

 

Puget systems did run into some inconsistent results when trying it with a pair of Pascal Titan X'es, but on a single card the difference was very minimal and depending on the game/benchmark.

https://www.pugetsystems.com/labs/articles/Titan-X-Performance-PCI-E-3-0-x8-vs-x16-851/

[Sfekke]

9 minutes ago, Captain Chaos said:

Nope, you'll need a Titan V before even noticing anything close to a bottleneck on x8. 

Cap'n is right here.

Having all those extra lanes really doesn't help with most current graphics cards, of course the RTX2080 could throw a wrench into that lane

 

You'll be fine with that GTX 1080Ti on 8x

 

@Captain Chaos just mentioning, it is 8x not x8 ..

[brob]

15 minutes ago, Genesis730 said:

I'm looking at getting the ROG Crosshair VII Hero (w/ Ryzen 7 2700x) and running RAID using the two PCIe 3.0 x4 M.2 slots.

It's my understanding that the GPU runs 8x, 4x, 4x lanes and the last 4x will go to the M.2 if used, leaving the GPU at x12 lanes (Which it will only use 8x lanes)

I'm using a GTX 1080ti to run 3 monitors. 2 of them at 1080 and the 3rd at 4k. Is there any concern of performance or bottlenecking at 8x lanes in the scenario?

Care to share why you are planning a RAID array of NVMe drives?

[dfsdfgfkjsefoiqzemnd]

11 minutes ago, Sfekke said:

just mentioning, it is 8x not x8 ..

hmm ... funny, I always wrote it as x8 ... and so does Puget Systems (see link in my above post).  Wikipedia's page on PCIe also puts the "x" in front of the number.

Will need to look into that. 

 

And it's not like you use a Belgian-only way of writing it, I'm in Antwerp myself

[brob]

5 minutes ago, Captain Chaos said:

hmm ... funny, I always wrote it as x8 ... and so does Puget Systems (see link in my above post).  Wikipedia's page on PCIe also puts the "x" in front of the number.

Will need to look into that. 

 

And it's not like you use a Belgian-only way of writing it, I'm in Antwerp myself

All motherboard specs that I can recall specify slots as <number of slots> x <number of PCIe lanes>. Like you I've always used x <number of PCIe lanes>.

[Genesis730]

5 hours ago, brob said:

Care to share why you are planning a RAID array of NVMe drives?

Putting 2x Samsung 970s in raid (Probably RAID 1) for the speed.

[andrewmp6]

Its been tested,Most games it runs the same as if it was 16x,I think one game was 5% slower but a card that fast you'll never see that 5% lost ever.

[Spotty]

10 hours ago, Genesis730 said:

I'm using a GTX 1080ti to run 3 monitors. 2 of them at 1080 and the 3rd at 4k. Is there any concern of performance or bottlenecking at 8x lanes in the scenario?

GamersNexus did some testing on this situation with a GTX 1080 with x16 lanes against the same GTX 1080 on x8 lanes.
https://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus

 

Tldr; Less than 1% difference in results, and that is within the margin of error for the tests.

Quote

These numbers are close enough in some instances – like the GTA V 58.3 vs. 58 FPS output – that they're effectively within margin of test error and do not definitively show a performance gap.

From a quick look, there is a little below a 1% performance difference in PCI-e 3.0 x16 and PCI-e 3.0 x8 slots. The difference is not even close to perceptible and should be ignored as inconsequential to users fretting over potential slot or lane limitations.

[brob]

11 hours ago, Genesis730 said:

Putting 2x Samsung 970s in raid (Probably RAID 1) for the speed.

Unless you are streaming 16K or something like that, the performance difference will be marginal at best. I'd suggest putting the money into a bigger drive or somewhere else in the build.