GPU in PCIEX4 instead of x16

mattydoughts · 16 Dec 2019 at 09:54

Hi All

I have built a new PC with a Ryzen 2600x and I have this Mobo https://www.overclockers.co.uk/gigabyte-b450-aorus-m-socket-am4-ddr4-matx-motherboard-mb-573-gi.html

A friend of mine told me to put the GPU in the PCIEX4 as it looks better and opens the case up (he likes to build a PC to look good full of lights etc). Does this effect the performance of the card? Surely it would be better in the x16 slot?

This is the GPU https://www.overclockers.co.uk/msi-...ddr5-pci-express-graphics-card-gx-35y-ms.html

Matt

stooeh · 16 Dec 2019 at 10:09

I expect in most games there will be a very small difference.

Razor Time · 16 Dec 2019 at 10:27

Yes the performance would be better in the 16x slot.

McManicMan · 16 Dec 2019 at 11:34

Maybe 1 or 2 fps, you won't notice

varkanoid · 16 Dec 2019 at 11:35

Depends on the case and where your PSU is if putting the GPU in the bottom PCIE slot it might reduce airflow to the GPU with it being to close to the top of the PSU. Top slot gives it more airflow and ensures its in a x16 slot for the most efficient speedwise.

pastymuncher · 16 Dec 2019 at 11:55

Put it in the top slot which is pci-e 3.0 16x compared to the bottom slot at pci-e 2.0 4x. Why sacrifice performance? When I build a new pc I want every last bit of performance I can get from it to maximise my "bang for buck".

Armageus · 16 Dec 2019 at 11:59

mattydoughts said:
A friend of mine told me to put the GPU in the PCIEX4 as it looks better

It doesn't - it just looks like you've put your GPU in the wrong slot

peterwalkley · 16 Dec 2019 at 14:45

Your friend seems to be interested in style over substance. Does he wear a Gucci belt ?

Jimmy Weirdarms · 16 Dec 2019 at 15:52

mattydoughts said:
Hi All
A friend of mine told me to put the GPU in the PCIEX4 as it looks better and opens the case up (he likes to build a PC to look good full of lights etc). Does this effect the performance of the card? Surely it would be better in the x16 slot?

The PCIe x4 slot there is a 2.0 slot, half the speed of equivalent 3.0 slots. So you are looking at an 8x slowdown in capability between the PCIe 3.0 x16 slot and that one.

Here is a test someone did with a 980Ti, on PCI 3.0 x16, PCI 2.0 x16 and PCI 3.0 x4, which concludes that there's not too much harm from PCIe 2.0 x16, but when they went down to 3.0 x4 thing started getting worse in benchmarks and some gaming measures - https://www.hardwaresecrets.com/pci-express-3-0-vs-2-0-gaming-performance-gain/
Your second slot on your board is half that speed, so I would imagine that yes, it will have a pretty major effect. Some other (quite old now) benchmarks with a Radeon Fury X showed a roughly 10% performance difference in games between PCIe 2.0 x4 and PCI 3.0 x16.

But hey! You have the hardware! Why not run a few benchmarks with the card in each slot, and tell us what you find?

Aretak · 16 Dec 2019 at 17:30

https://www.techpowerup.com/review/nvidia-geforce-gtx-1080-pci-express-scaling/

I doubt an RX 590 is going to lose much, if any performance no matter where you put it.

pastymuncher · 17 Dec 2019 at 11:12

Going by that chart the GTX1080 has a 13% performance hit at 1080p going from pci-e 3.0 16x down to pci-e 2.0 4x which is quite a big hit. I would expect the RX 590 to have a similar hit and I certainly wouldn't want to lose that much performance.

Jimmy Weirdarms · 17 Dec 2019 at 11:14

So that 1080 loses 8-13% depending on what resolution it's driving when comparing 3.0 x16 to 2.0 x4, and which game it's playing. We have a 980Ti losing a few percent in the tests I linked to, I can find reddit threads showing a 1070 was affected by 10% ish in a similar situation.

I'd say it's very possible the 590 loses some performance, yes.

jonathan_phang · 17 Dec 2019 at 15:07

I think it will just look odd personally. Performance wise it will suffer, but the airflow is going to get killed, which is never good. If you really must go for looks, then consider a vertical GPU mount, on the presumption that you arent putting anything else in the other PCIe slots

something daft already!! · 17 Dec 2019 at 15:10

There is not one jot of difference when I run my 1070 in x8 or x16 mode. Not tried x4 though.

Jimmy Weirdarms · 17 Dec 2019 at 20:38

something daft already!! said:
There is not one jot of difference when I run my 1070 in x8 or x16 mode. Not tried x4 though.

The choice hete is between PCIe 3.0 x16 and PCIe 2.0 x4, which is a drop of eight times the speed.

Your 1070 is probably on PCIe 3.0 x8? That's still four times as fast as the PCIe 2.0 x4 slot this poster is using.

something daft already!! · 17 Dec 2019 at 20:43

No, it's on a x16 slot. I was trying out something, popped in the x8 slot and got exactly the same performance. I'm not say x4 will not be slower, more that x16 seems unnecessary still as yet. Maybe it has an impact on faster GPUs.

tyler_jrb · 17 Dec 2019 at 21:48

Put in the x16 slot. You will lose performance using a x4 2.0 slot for sure. No real reason to put it in the lower slot, just would look odd in my opinion as the card would look out of place.

varkanoid · 17 Dec 2019 at 21:58

Jimmy Weirdarms said:
The choice hete is between PCIe 3.0 x16 and PCIe 2.0 x4, which is a drop of eight times the speed.[/COLOR]

something daft already!! said:
No, it's on a x16 slot. I was trying out something, popped in the x8 slot and got exactly the same performance. I'm not say x4 will not be slower, more that x16 seems unnecessary still as yet. Maybe it has an impact on faster GPUs.

Confirm before you say there is no difference.

Yrkoon · 18 Dec 2019 at 00:24

mattydoughts said:
Hi All

I have built a new PC with a Ryzen 2600x and I have this Mobo https://www.overclockers.co.uk/gigabyte-b450-aorus-m-socket-am4-ddr4-matx-motherboard-mb-573-gi.html

A friend of mine told me to put the GPU in the PCIEX4 as it looks better and opens the case up (he likes to build a PC to look good full of lights etc). Does this effect the performance of the card? Surely it would be better in the x16 slot?

This is the GPU https://www.overclockers.co.uk/msi-...ddr5-pci-express-graphics-card-gx-35y-ms.html

Matt

i don't think you're friend is been the sharpist tool in the book by asking for that on looks... it just sounds dumb to me, there is a reason that slot is the highspeed one, designed for gpu's

meh im drunk lol

Aretak · 18 Dec 2019 at 01:05

pastymuncher said:
Going by that chart the GTX1080 has a 13% performance hit at 1080p going from pci-e 3.0 16x down to pci-e 2.0 4x which is quite a big hit. I would expect the RX 590 to have a similar hit and I certainly wouldn't want to lose that much performance.

The need for PCIe bandwidth increases as the power of the GPU increases. They did the same testing with a 2080 Ti and found that the drop in performance was much larger, with it losing 14-22% performance (depending on resolution) by the time you get down to PCIe 2.0 4x, so it's clearly not a static across the board degree of performance being lost.

https://www.techpowerup.com/review/nvidia-geforce-rtx-2080-ti-pci-express-scaling/6.html

However, that would also mean that you're going to see less of a performance drop if you use a less powerful card. The RX 590 isn't even close to a GTX 1080, so I'd expect it to lose a lot less performance (if any) from being denied as much bandwidth. Of course, some actual, credible A/B testing would be needed to know for sure, and to know where the actual breakpoint in GPU power is for each.