Help, Sapphire rx 480 works at pcie 3.0 x4 instead of x16

Evrim

Junior Member
Feb 2, 2017
2
1
1
Hey, I recently bought a Sapphire nitro+ rx 480 8gb oc. I have a gigabyte z77-ds3h mobo, i5 3570k pcu (not oced) and thermaltake litepower 600w psu : http://www.thermaltake.com/products-model.aspx?id=C_000...

I have struggled for a few days to make the gpu work at the topmost pcie 3 x16 slot. It was working in the bottom slot which is pcie 2.0 x4 but not in the pcie 3.0 one.

After clearing cmos, updating bios and fiddling with the bios settings I have managed to make it work with the pcie 3.0 slot but now it is only wowking at x4. It stays at pcie 1.1 x4 when idle, and switches to 3.0 x4 when under load but couldn't manage to rise it higher. Also I am pretty sure gpu is well fit in the slot.

After a restart yesterday, my gpu started to work at pcie 3.0 x16. However after a few seconds of load it stopped working alltogether. It continued with all kinds of problems like not being recognised at the start, crushing windows, bsods etc, until I switched pci slot back to 2.0 and then to 3.0 again. It is working at 3.0 x4 fine again. Guess I will need to replace my mobo or psu but I don't know which causes the problem. But I am more and more worried about my psu as it has 12v dual rail with 25 and 20 amps respectively.

I am also willing to leave it like that but I am not sure about a potential bottleneck.

And rma conditions are pretty terrible in my country so I prefer solving it inhouse if that is possible.

Sorry for the long post, any help is greatly appreciated
 

gradoman

Senior member
Mar 19, 2007
847
435
136
The changing bus speed sounds like typical behavior similar to how modern GPUs up- or downclock according to load to conserve power. As for the crashing at 16x, could be your PSU is of questionable quality. I can't even find a review of the model and from some comments, it seems to be a very low-end model. If you can get a hold of another PSU to test, that would help to possibly eliminate one of the potential failure points.

Since you have motherboard with video out, you can test to see if you get crashes without the GPU installed by running some games and perhaps a CPU stress test.
 

Evrim

Junior Member
Feb 2, 2017
2
1
1
UPDATE : So I replaced my psu with a Seasonic S12II. The problem still persists but at least I am not worried about frying my gpu:) I tried the gpu on another machine and it works at 3.0 x16 without any problems there. So I think my mobo is the problem however I am not really willing to replace it for the moment. I am planning to use the gpu at the lower pcie to prevent any damage from the broken slot even when the top slot works 2x the speed. (ps: it works fine at 3.0 x4 at the top slot however sometimes at restart it switches to x16 and crashes a few times until it reverts back to x4 by itself)

I haven't noticed any performance issues using pcie 2.0 x4, I hope I am not terribly wrong about that.

My cpu and mobo's gpu doesn't crash with stress tests, and I have set the Peg Gen to 3.
 
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jlee

Lifer
Sep 12, 2001
48,511
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UPDATE : So I replaced my psu with a Seasonic S12II. The problem still persists but at least I am not worried about frying my gpu:) I tried the gpu on another machine and it works at 3.0 x16 without any problems there. So I think my mobo is the problem however I am not really willing to replace it for the moment. I am planning to use the gpu at the lower pcie to prevent any damage from the broken slot even when the top slot works 2x the speed. (ps: it works fine at 3.0 x4 at the top slot however sometimes at restart it switches to x16 and crashes a few times until it reverts back to x4 by itself)

I haven't noticed any performance issues using pcie 2.0 x4, I hope I am not terribly wrong about that.

My cpu and mobo's gpu doesn't crash with stress tests, and I have set the Peg Gen to 3.
https://www.pugetsystems.com/labs/articles/Impact-of-PCI-E-Speed-on-Gaming-Performance-518/

It doesn't make much of a difference.
 

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