[SOLVED] My GPU only runs at 12 gb/s pcie speed.

ludvigbuskthomasen

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Aug 20, 2017
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So I have a 3080 rtx GPU and i recently found out I had put it in the wrong pci-e slot, an 4x one. So i changed it to 16x (CPU lanes) 3.0 gen. I read online that i should now get 16 gb/s speed ideally. I just took a 3dmark test that tests the PCIE speed, and it gave me a speed of only 12,8 gb/s. My motherboard and cpu both supports 16x 3.0 and i don't have any other things taking up pcie slots. I did read online that some people were talking about ssd's taking up some lanes but to my understanding that would only be if the ssd's are installed in a pcie slot right?

Is this normal or am i not seeing something?

Thank you

Specs:
GPU: 3080 ASUS TUF non-oc
CPU: i7-9700k
RAM: 16 GB 3600 mhz
Motherboard: z390-a pro

Btw, should i enable resizable bar? is it just a waste or would i actually be seeing a benefit?
 

JWNoctis

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Jun 9, 2021
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16GB/s (actually slightly less) is theoretical. Some overhead, like yours, is normal.

Resizeable BAR certainly won't hurt, and won't cost you any more if your system supported the setup. You would have to do a benchmark comparison to see any actual benefit, though.
 

JWNoctis

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Jun 9, 2021
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16GB/s (actually slightly less) is theoretical. Some overhead, like yours, is normal.

Resizeable BAR certainly won't hurt, and won't cost you any more if your system supported the setup. You would have to do a benchmark comparison to see any actual benefit, though.
 

ludvigbuskthomasen

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Aug 20, 2017
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16GB/s (actually slightly less) is theoretical. Some overhead, like yours, is normal.

Resizeable BAR certainly won't hurt, and won't cost you any more if your system supported the setup. You would have to do a benchmark comparison to see any actual benefit, though.
Thank you for your answer.
I found out my CPU doesn't support resizable bar unfortunatly.
So 12,3 gb/s is normal even though it seems a bit low i guess. Can i be 100% sure that nothing is eating up the pci-e lanes or speed when alll my pcie slots are empty, except the one with my graphics card?
 
This is something you don't have to worry about and honestly I don't know why it's even a benchmark on 3DMark other than to say, verify that even though a video card appears to be a x16 card, it's really only an x8 card (e.g., the Radeon RX 5500 cards). Except this is something can verify with GPU-z anyway.

Even the RTX 3080 can down to PCIe 3.0 x4 and lose not that much performance.
 
Thank you for your answer.
I found out my CPU doesn't support resizable bar unfortunatly.
So 12,3 gb/s is normal even though it seems a bit low i guess. Can i be 100% sure that nothing is eating up the pci-e lanes or speed when alll my pcie slots are empty, except the one with my graphics card?
The z390 chipset uses a dedicated 3.0 16 lanes straight from the cpu. So, basically no. And m.2 drives will just disable Sata ports on that particular motherboard.
 

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