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.

 

[Imperat0r]

Rx 5700 XT will draw 225 w.
Rx 6700 XT will draw 230 w.
AND....RX 6600 XT will draw only 160w.

So i think you need to focus on a 6600XT that will do it's job for less power.
And for sure with 6600XT your current PSU will be in order.

 

[The Historical Fidelity]

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.

I would advise against the 5500 xt due to the 4 GB vram. Honestly I wouldn’t get anything lower than a 5700 non-xt with 8 GB vram (power usage is 180w which is 45 watts less than 5700 xt and won’t overload your power supply), and check prices of the 6650xt in your country, here in the U.S. they are going for $219 with free shipping and would remain relevant for many years before you’d need to upgrade given you felt your 1060 was adequate until now. If these are too expensive then look at the 5600xt with 6GB, it’s not the recommended minimum 8GB for modern games but 6 is still better than 4.

 

[jeremyj_83]

I would advise against the 5500 xt due to the 4 GB vram. Honestly I wouldn’t get anything lower than a 5700 non-xt with 8 GB vram (power usage is 180w which is 45 watts less than 5700 xt and won’t overload your power supply), and check prices of the 6650xt in your country, here in the U.S. they are going for $219 with free shipping and would remain relevant for many years before you’d need to upgrade given you felt your 1060 was adequate until now. If these are too expensive then look at the 5600xt with 6GB, it’s not the recommended minimum 8GB for modern games but 6 is still better than 4.

The original post mentioned the 5500XT 8GB version as what they are looking at.

 

[The Historical Fidelity]

The original post mentioned the 5500XT 8GB version as what they are looking at.

Ahh missed that, however I honestly don’t think a 5500 xt has the horsepower to play any game that requires more than 4GB so my suggestion remains that minimum RX 5700 and recommended RX 6650 xt.