AMD RX 6500 XT PCIe 3.0 vs. 4.0 Tested

[harlan4096]

Up to 40% lower performance on PCIe 3.0.

AMD's new Radeon RX 6500 XT graphics card is proving to be rather divisive. On the one hand, some people herald it as a great win for gamers who have been unable to acquire any of the best graphics cards due to miners and scalpers snapping them all up. However, others point to the major cuts to the hardware specs and the resulting poor performance, coupled with a relatively high launch price, as being a far cry from what we'd normally see in a supposedly "budget" GPU. But there's another area of concern: a budget GPU is more likely to be used as an upgrade in an older PC, which means the x4 PCIe 4.0 connection might become even more of a problem.

We already had test results from our updated GPU test PC, which has a Core i9-12900K CPU, MSI Pro Z690-A WiFi DDR4 motherboard, and 32GB of DDR4-3600 memory. We also have our previous generation GPU test PC, with a Core i9-9900K, MSI MEG Z390 Ace motherboard, and the same 32GB DDR4 memory kit. The key difference is that the Z390 platform only supports PCIe 3.0 while the Z690 supports up to PCIe 5.0 hardware (and is backward compatible with 4.0).

To verify that the CPU itself wasn't a major contributing factor, we ran both the RX 6500 XT and GTX 1650 Super through our new gaming test suite on both PCs. We tested at 1080p medium, where the 4GB VRAM should be sufficient on both GPUs, and also at 1080p ultra, which will push gaming beyond 4GB. Here are the results.

The GTX 1650 Super, which doesn't support PCIe 4.0 but does have a full x16 interface, shows relatively similar performance. Interestingly, the 9900K system actually outperformed the 12900K just slightly overall, with individual gaming results showing a +/-8% spread (but typically falling closer to 1–2%). So far so good, then, as the CPU and motherboard differences don't seem to impact things too much.

Now let's talk about the RX 6500 XT. On average, performance dropped around 8% at 1080p medium. We'll include the individual gaming results below, but we saw everything from a 26% drop (Borderlands 3) to an 8% increase (Horizon Zero Dawn). We were a bit time-constrained and the differences in testbed hardware can potentially skew results, but it certainly looks like the slower PCIe link speed had a noticeable impact.

That impact was felt a lot more at 1080p ultra settings, which exceeded the 4GB VRAM. That's to be expected because going beyond your card's VRAM means pulling data over the PCIe bus, and a slower link there becomes much more painful. This time, the 9900K was on average 23% slower, with individual game results ranging from 4% slower (Horizon Zero Dawn) to as much as 35–40% slower (Borderlands 3 and Forza Horizon 5).
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