Question GPU bandwidth during gaming

ArcanumSteamwork

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Oct 8, 2016
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Hi, probably it is a dumb question but I am trying to rationalize the number of PCI-E cards I can use on my motherboard.

Many intel CPUs support PCI-E 3.0 16 lanes for a total of 15.75 GB/s, right?

I have read that, currently, the GPU uses max a 8x PCI-E even when connected to a 16X, therefore they should use max 7.88 GB/s of the bandwidth.
If this is correct I will have another 7.88GB/s to allocate through the other PCI-E cards.
My question is: because the use of the bandwidth varies according to the game and the setting, how can I find an average value they use?
If I am missing something in the reasoning please explain it to me
 

ArcanumSteamwork

Honorable
Oct 8, 2016
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Worst case scenario, for gaming. Can any game saturate the bandwidth if played at 60 fps and 1080p? If no, is there a place where I can find information about the average use of the bandwidth with those settings? Basically, if I know that a normal bandwidth during gaming is 6GB/s, I can almost surely predict that I will be able to use about 1GB/s elsewhere, for NVMe for example, without risking bottlenecking the GPU or vice-versa
 
If there's activity on the PCIe bus to the graphics card, it's doing one of three things:
  • Sending commands/responses back and forth
  • Loading in assets
  • Swapping data between itself and system memory
The first one shouldn't be a problem unless you have an infinitely powerful GPU and CPU. The second one is a normal part of the process. The third one is a problem because it means the video card ran out of available VRAM and is using system memory as a temporary storage (it's the GPU equivalent of the computer using the page file because it ran out of RAM).

As far as your concerns regarding bandwidth utilization, every PCIe device has it's own set of lanes. What the GPU does does not affect the NVMe drive.
 

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