Interesting review of the new Radeon RX 6500 XT & only being PCIe 4.0 compatible

[Blunt]

Quote

With PCIe 4.0 you get roughly 2 GB/s of bandwidth per lane, giving the 6500 XT a ~8 GB/s communication link with the CPU and system memory. But if you install it in a PCIe 3.0 system that figure is halved, and this is where you could start to run into problems.

 

But this isn’t about the extreme cases, where we dropped to unplayable performance, it’s about the card being noticeably slower when using PCIe 3.0 x4 bandwidth. In the case of the 5500 XT, we went from 82 fps on average at 1080p in the 12 games tested to just 57 fps, that’s a huge 30% decline in performance.

 

The Radeon RX 6500 XT is likely to face the same problem, but as we mentioned in the introduction, it's based on a different architecture, so maybe that will help. But if we see no change in behavior, the 6500 XT is going to end up being a disaster for PCIe 3.0 users and at best a mixed bag using PCIe 4.0.

 

https://www.techspot.com/review/2396-pcie-bandwidth-test/