Question PCI-E 3.0 Question

SpaceWizardNinja

Commendable
Dec 2, 2019
6
0
1,510
Ok so, after watching a recent LTT video of a wife build off with BitWit, they mentioned how one of the builds may be not getting the full performance from installing their GPU in the second, as oppose to the top-most, PCI-E slot. My question is two fold; First, I'm running an RTX 2070 into a MSI MPG Z390 Gaming Pro Carbon AC LGA 1151 (300 Series) in my second PCI-E 3.0 x 16 slot for purely ascetic reasons (as oppose to the top-most). By doing this am I sacrificing any performance? Secondly, my understanding is a PCI-E 3.0 x 16 slot is a PCI-E 3.0 x 16 slot is a PCI-E 3.0 x 16 slot. Am I making incorrect assumptions? Did I perhaps misinterpret the video I watched and there is a reason specific to that MOBO used in the video why one PCI-E was preferential to another? Side note, I could not see in the video is the GPU in question was installed into a x-16 or x-1 PCI-E. Any help and/or education on the subject would be greatly appreciated. Thank you for your time and knowledge.
 
my understanding is a PCI-E 3.0 x 16 slot is a PCI-E 3.0 x 16 slot is a PCI-E 3.0 x 16 slot. Am I making incorrect assumptions?

You are incorrect. The slot doesn't change. The 16x slot is a 16x slot. But it might not have 16 lanes attached to it. The first slot when used alone has all 16 lanes attached to it. But in many boards when you plug something into the second slot it drops down to x8 lanes. This is the "not full performance" they mentioned in the video. It mostly doesn't matter however as modern cards don't even exceed the bandwidth that PCIe 2.0 16x provides. Which happens to be the same amount as PCIe 3.0 8x. If it works and you are happy with it, keep going.
 
Fantastic! For future reference, is there a way I can distinguish how many lanes an given PCIe x16 slot has? I don't see myself needing another slot in the near future, but some of the newest storage solutions via PCIe have me interested.
 
You have to check the manual.

Someone made a mining board once. Had 7 or 8 PCIe 16x slots, but each slot was only 1x electricially. That way you could hook up as many video cards as you can. They do the work on the card, they don't need a lot of bandwidth.