PCIe lanes used by graphics card

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rcw600

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Jun 30, 2011
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I'm wondering if anyone knows how CPUID Hardware Monitor works when it displays bus usage for the GPU? This is shown as a percentage, but does it take account of whether the card is in a 8 or 16 lane slot? For example, if I have the card in a slot configured with 8 lanes and the bus usage is showing as 25%, does that mean 25% of the maximum bandwidth of 8 lanes, or 25% of the maximum bandwidth of 16 lanes that the card can use in a x16 slot? What I am trying to understand is if my card can manage with 8 lanes or needs the full 16, for the games and apps that I use. If it doesn't saturate 8 lanes with my usage that would give me more flexibility with other PCIe devices (I've got four NVMe SSDs and thought I might give RAID a go, using a PCIe riser card). My system is Asus Crosshair viii Formula (which is a PCIe 4.0 board), Ryzen 7 3700X and GeForce RTX 2080ti.

I'm also interested to know if a PCIe 4.0 card (in a PCIe 4.0 motherboard) would be better. I understand PCIe 4.0 has double the bandwidth of PCIe 3.0, so does that mean a PCIe 4.0 GPU would get the same bandwidth using 8 lanes in a PCIe 4.0 motherboard as a PCIe 3.0 card/motherboard would get when using 16 lanes?

Thanks for any advice!
 
I don’t have the answer for your first question, but I’d imagine it’d be easy to figure out with a little A/B testing, assuming you can change your PCIe configuration in the BIOS settings.

You second question: yes. 8x 4.0 is the same as 16x 3.0 (for a 4.0 device).
 
BinarySynapse said:
I don’t have the answer for your first question, but I’d imagine it’d be easy to figure out with a little A/B testing, assuming you can change your PCIe configuration in the BIOS settings.

You second question: yes. 8x 4.0 is the same as 16x 3.0 (for a 4.0 device).
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Thanks for that quick reply - can you elaborate on the kind of testing you mean? Sorry but I don't know what you mean by 'A/B testing'!
 
Run your workload at 16x (condition A). Then run it again at 8x (condition B). Compare the results.
 
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