Difference in performance PCIe Gen 5 lot at x8 vs x16 on Gigabyte RX 7800 XT 16 GB

[East Coast Dan]

Good morning folks,
First time poster here. These are the parts affected by the change I want to make:

Asus TUF Gamin X870 Plus Wifi
Gigabyte RX 7800 XT 16 GB
Sabrent Rocket 5 Gen 5 Nvme

Looking to put in a second Gen 5 drive in the other Gen 5 Slot, this will reduce the PCIE Gen 5 slot to x8 instead of x16. How bad will this effect graphics performance?

[Ha-Satan]

Keep in mind that the 7800 XT is a PCIe Gen 4 GPU, so it will only ever use PCIe Gen 4 with however many lanes it has available. So if you reduce the PCIe slot to 8 lanes, it will be 8 PCIe gen 4 lanes for the 7800 XT.

 

I'm unable to find a test of the 7800 XT using PCIe 4.0 16 lanes vs. PCIe 4.0 8 lanes, but I did find at least a few tests of the 7800 XT with PCIe 4.0 16 lanes vs. PCIe 3.0 16 lanes:

 

 

Theoretically, IIRC PCIe 3.0 16 lanes should give the same throughput as PCIe 4.0 8 lanes, so you could sort of use this as a rough approximate. That said, I wouldn't put too much stock in this data as (a) I don't know if I can trust this video and (b) I'm relying on possibly shaky logic here to make this comparison.

 

Quick question - what are you wanting to do with the second NVMe drive? It's possible that maybe you really don't need a Gen 5 drive for what you're doing, in which case you don't necessarily need to worry about the lane issue for the GPU.

 

EDIT: Also, what CPU do you have? This matters because it might change how the slots work.

[East Coast Dan]

I have a Ryzen 7 9800X3D with 64 GB of DDR5

 

[Ha-Satan]

18 minutes ago, East Coast Dan said:

I have a Ryzen 7 9800X3D with 64 GB of DDR5

 

OK, then you don't need to worry too much about it - you should get the full capacity of the board. So then my next question is - what are you doing with your PC that demands PCIe 5.0 speeds on your SSD? If it's gaming, then you should just get a PCIe 4.0 SSD and put it in the M.2_3 slot so that you don't cut down bandwidth to the GPU.

[East Coast Dan]

I use PC for work and personal use, so I already have a Gen4 in slot M.2_3 for work and the Gen5 in slot M.2_1, want to get another one for storage and need the 2nd PCIe slot for extra USB ports for my front I/O on my Corsair 7000D Airflow 2024