PCI-E Shared Bandwidth Question

Name · 11 Apr 2023 at 20:45

Hi there,
I've recently purchased a B650 MSI carbon wifi board. Upon reading the manual it states that the main PCI-E X16 slot shares bandwidth with the 2nd and 3rd M.2 slots and if populated with ssds then the PCI-E x16 slot runs at x8. Shown below

My question is: can my RTX 3080 still run at acceptable speeds at Gen 4.0 x8 speed ? Some have told me I'll be fine unless heavily benchmarking. Others have said this is rubbish design and to get a refund - your thoughts?

Tetras · 11 Apr 2023 at 20:57

I suspect that they did this so that the board can support 4 M.2 slots, which is an unusual number for a B650 board.

To answer your question: you'll lose a few percent at most (article, PCI-E 3.0 is equivalent bandwidth to 8 lanes).

Name · 11 Apr 2023 at 21:11

Tetras said:
I suspect that they did this so that the board can support 4 M.2 slots, which is an unusual number for a B650 board.

To answer your question: you'll lose a few percent at most (article, PCI-E 3.0 is equivalent bandwidth to 8 lanes).

Ah yes thanks for the article, upon reading it got me looking at a few other articles/video benchmarks it appears the impact can be as little as 3-5%

I was worried that I was going to reduce performance by 50% or something

quite pleased now as I got it under 300 smackers during an easter sale (which is still outrageous for a mobo)

Tetras · 11 Apr 2023 at 22:01

Name said:
Ah yes thanks for the article, upon reading it got me looking at a few other articles/video benchmarks it appears the impact can be as little as 3-5%

I was worried that I was going to reduce performance by 50% or something quite pleased now as I got it under 300 smackers during an easter sale (which is still outrageous for a mobo)

Nah, not even pci-e 1 would be that bad

You could just use slots 1 and 4, depends how many m.2 you have I guess.