The performance of AMD Radeon is likely to visibly limited on PCle Gen 3 platforms. It has been tested that AMD Radeon RX 5500XT 4GB on PCle Gen4 x8 is on average 49% faster in comparison with Gen3 x4.
A potential problem is being investigated by the Hardware Unboxed in the upcoming entry level Radeon card which is due in just 2 days.
As reported earlier by us, the limited PCle Express to four lanes will be featured by the Radeon RX 6500XT graphics card. This card is based upon the fourth generation of PCI Express due to which it can provide just as much bandwidth as the eight lanes on Gen3 standard.
This may not be considered as an issue immediately. However, for a budget GPU such as RX 6500XT, there are chances that the users who are considering this card may still feature PCle Gen 3 system meaning even less bandwidth with only four available lanes.
Hardware Unboxed can not post their RX 6500XT results as they are not allowed to do so due to the review embargo but still they can use their previous gen models such as Radeon RX 5500XT based upon Navi 14 GPU just to see if there is a performance bottleneck in the coming from the Gen3 interface.
A reviewer has noticed that there are more chances of bandwidth issues with the 4Gb cards rather than the 8Gb cards as some resources will be stored in the video memory instead of being extracted constantly from the system memory or storage. There were two variants in which RX 5500 XT was available, 8Gb and 4Gb memory making it a perfect competitor or candidate for this type of test.
It has been shown by the results that games that were already affected by the limited avRAM of the graphics card were having more chances to show a double digit performance impact from the bandwidth constrained interface. So, it can be concluded that the average framerate at 1080p resolution will be reduced by PCle 3.0 x4. The Gen4 x 8 will be 49% faster than the Gen3 x 4 however there was no graph for PCle 40, x4 vs 3.0 x4.
RX 6500XT has been designed based on the latest RDNA2 architecture and features an Infinity Cache of 16MB. Though not being able to have a considerable impact, both of these upgrades will be able to counter the bandwidth problem to some extent.