Question Performance impact of a PCIe 4.0 x8 GPU on a PCIe 3.0 x16 mobo

[sys-256]

Hi everyone,

I built my PC in february 2021 with a ryzen 5 2600 (CPU), Gigabyte GeForce GTX 1050 Ti Windforce OC 4G (GPU) and ASUS ROG Strix B450-F Gaming (mobo). I want to upgrade to a (2nd hand) ASUS ROG Strix RX 5500 XT 8G GAMING OC as it offers better performance, and because I want to start using wayland (I'm a linux user).

The issue is that the RX 5500XT has a PCIe 4.0 x16 slot, but only uses 8 lanes, and my motherboard has a PCIe 3.0 x16 slot. Does this mean that the RX 5500XT will run at PCIe 3.0 x8 speeds? Also would that mean that I only get half of the FPS it's capable of, or is the difference negligible? A (higher end) GPU that uses 16 PCIe lanes like the RX 5700XT is still within my budget, but I'm afraid of getting a CPU or PSU (Corsair RM550x) bottleneck. And I dont really need the extra performance anyways since I only play CS2 and some indie games.

Thanks in advance for the replies!

 

[The Historical Fidelity]

That is correct, the 5500xt only has 8 physical pci-express 4 lanes. These lanes can operate at legacy speeds like pci-express 3, however, you will achieve half the intended bandwidth that the card was designed for. In reality, you are maybe losing 5-10% maximum and often 1-3% using pci-e 3 because the 5500xt does not even saturate 8 pci-e 4 lanes.

If the price difference is not too steep, the 5700xt is much better performance value and does not fully saturate pci-e 3 x16 lanes so performance difference with pci-e 4 will be negligible. If you can find a 6600 or 6600xt for a good price, they bring even greater performance value.

 

[Imperat0r]

As you aleady told us, your mainboard support only PCIe 3.0.
This is the max speed of your PCIe and your video card will use from those 16 lanes only 8.
So yeah, indeed your card will work in PCIe 3.0 - 8 lanes.
And yes, you are almost at max with your CPU.
But on the other hand RX5700 work very good also in your system and will squeeze the last frame from it.
But your PSU is too low for RX5700.
The video card will draw alone 225W.

read the article:
https://www.tomshardware.com/reviews/amd-radeon-rx_5700-rx_5700_xt,6216-5.html

 

[jeremyj_83]

It will run at PCIe 3 x8 speeds. However, with the 8GB VRAM the performance loss is minimal vs an x16 link.

 

[sys-256]

Thanks everyone for the quick replies! The 6600's and 6600xt's go for over 200 euro, where as the 5500xt is only 90 euro. The 5700xt is 150-170 euro but then there's the PSU issue, so I'm gonna get the 5500XT.

 

[jeremyj_83]

Thanks everyone for the quick replies! The 6600's and 6600xt's go for over 200 euro, where as the 5500xt is only 90 euro. The 5700xt is 150-170 euro but then there's the PSU issue, so I'm gonna get the 5500XT.

With a 550W PSU you can run a 6700XT if you wanted. You don't need a huge PSU to run mid range GPUs.