Radeon RX 6400 graphics card loses about 14% performance when using PCIe 3.0 interface

TechPowerUp resource recently tested the new AMD Radeon RX 6400 graphics adapter on the legacy PCIe 3.0 interface to measure performance drops compared to PCIe 4.0, and it turns out it stems from an unorthodox GPU configuration adapted for four PCIe lanes.
The average performance drop was over 14%, depending on resolution.The AMD Radeon RX 6400 is an entry-level graphics gas pedal for the desktop segment with a Navi 24 core, originally designed for laptops, like its big brother, the Radeon RX 6500 XT.
This GPU contains only four PCIe 4.0 lanes as a manufacturing cost-cutting measure.The Radeon RX 6400 has a roughly 13% reduction in cores and memory bandwidth over the Radeon RX 6500 XT.
The graphics card has only 768 cores and 128 Gbps of memory bandwidth, thanks to a reduction in GDDR6 speed to 16 Gbps.
However, the memory capacity remains unchanged at 4 GB.
But the main strength of the Radeon RX 6400 is power consumption, it has half the power of the Radeon RX 6500 XT 53W, making this GPU very useful in small budget systems that can't power higher-end GPUs with an auxiliary power cable.24 games were tested and the Radeon RX 6400, running on the PCIe 3.0 bus, had an average performance drop of 14% at both 1080P and 1440P compared to PCIe 4.0.
The 4K results were even worse, with a 23% performance deficit.
However, it will undoubtedly make a big difference, as the Radeon RX 6400 offers unplayable FPS at any PCIe generation.Some of the worst results included racing simulator F1 2021 and shooter Doom Eternal, which had performance differences as high as 79% and 43% at 1080P.
Fortunately, almost all other gaming applications tested were in the 14% range or lower, but these two games show just how intense some PCIe gaming engines can really get.Testing the Radeon RX 6500 XT showed a performance gap of 13% for PCIe 3.0 versus PCIe 4.0.
The Radeon RX 6400 can't avoid the Navi 24's four-lane limitations, even though the GPU itself is slower.
The PCIe 3.0 Radeon RX 6400 was nearly 20% slower than the GeForce GTX 1650, which runs on the same PCIe 3.0 interface and on a much more optimal x16 lane configuration.
However, when installed in a PCIe 4.0 interface, the Radeon RX 6400 performs similarly to the GeForce GTX 1650.Consumers choosing the Radeon RX 6400 need a PCIe 4.0 platform to avoid serious performance degradation from the PCIe 3.0 bus.
The biggest problem is that most systems are still on PCIe 3.0, and gamers who are likely to buy a Radeon RX 6400 are using it on an older system.
If you don't have PCIe 4.0, the best alternative is Nvidia's GeForce GTX 1650 or even the older Radeon RX 570, which is faster than the Radeon RX 6400 and does not require PCIe 4.0 to unlock its full performance.