Question PCIe versions and lanes speedj

Apr 29, 2019
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I have a question about PCIe lanes speeds with regard to backward compatibility. I want to build a X570 Ryzen PC but the motherboard I choose (Asus Rog X570-i) will likely share the GPU with the back ssd port. My question is as follows, when I install an nvme ssd and a GPU will the speed remain at the level of PCIe 3 x16 when it’s used in a PCIe 4 port or will it be lowered to PCIe 3 x8 as only 8 lanes will remain. I understand that it may be somewhat confusing to understand but it’s very important to understand this before I decide what to buy. The motherboard configuration is based on the previous X470 and B450 ones.

Thanks
 

13thmonkey

Titan
Moderator
you need to wait for the specs to be fully released. My understanding is that the CPU has 4 PCI lanes for storage, and the PCH has 4 lanes for storage, so I can't see why they'd use any of the GPU lanes. Anandtech has an article of X570 as we understand it at the moment.
 
Reactions: DMAN999
Apr 29, 2019
5
0
10
0
you need to wait for the specs to be fully released. My understanding is that the CPU has 4 PCI lanes for storage, and the PCH has 4 lanes for storage, so I can't see why they'd use any of the GPU lanes. Anandtech has an article of X570 as we understand it at the moment.
Do you know how it works for PCIe 3 when only 8 lanes are available and a PCIe 2 device is used? I did not find any information on this when looking at the X470-i and B450-i motherboards.

Edit:
I mentioned on using the GPU lanes as Asus did exactly than with the older itx motherboards - if a second storage device is used it will use 8 of the GPU lanes, not the chipset ones. If they change it this time to PCH then that would be best, but I still would like to know how it works for older devices.
 
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