AMD RX 6400 graphics: does it perform better under PCIe 3.0 or under PCIe 4.0?

This question that seems a bit strange, actually on this graphics card is quite important. The RX 6400 has a PCIe x4 configuration, which is a letter part of the usual configuration of gaming graphics cards. The reason for cutting back on the PCIe lanes used is to simplify the design of the GPU itself.

AMD RX 6400, a simple and, in principle, cheap graphics card

The RX 6400 graphics card ranks as the worst of the RX 6000 family based on the RDNA2 architecture. It is focused on an audience that wants to play casually and does not care about the FPS rate.

This graphics card has 768 Stream Processors, 12 Ray Accelerators, 48 ​​Texture Units and 32 ROPs. The graphics card locks at a Gaming frequency of 2039 MHz and can reach 2321 MHz in Boost mode. It is accompanied by 4GB GDDR6 at a frequency of 16 GHz, with a 64-bit interface and a bandwidth of 128 GB/s.

This graphics card uses a PCIe 4.0 x4 connection, so it does not use all the pins of this connection interface. A fact that may seem insignificant, but that becomes important if we take into account the volume of data that can be transmitted. PCIe 4.0 x4 allows up to 7.88GB/s of datawhile PCIe 3.0 x4 allows up to 3.94GB/s of data.

As we can see, we are halving the amount of data that is transmitted. This, of course, will end up affecting performance. The amount of information that can be exchanged with the processor is less and it implies a drop in performance.

How much does the performance of this graphics card get worse?

According to the test carried out by TechPowerUp, a average yield loss of 14%. For the test, 25 different games have been tested in 1080p, 1440p and 2180p resolutions. Obviously, since this graphics card only has 4GB of VRAM memory, the tests in 1440p and 2180p are quite uninteresting, since the performance will be very low in said resolutions.

The most noticeable performance loss is in the Assassin’s Creed Valhalla and God of Warwhere drops up to 35% performance. In DOOM Eternal you lose up to 30% performance. Note that in some games the difference is practically imperceptible, hence the general performance loss measurement is 14%.

having low VRAM memory, what the operating system does is free up space by sending the information from the graphics memory to the system’s main memory. When information needs to be retrieved, since bandwidth is limited, there is a great impact on performance.

But with no load on the VRAM, the clipped bandwidth is very important. The renderer plays a big role in things like rendering or how you animate the world. Instructions must travel between the processor and the graphics card. If there is a bottleneck (as is the case) latencies increase. As the time to perform the task increases, the amount of FPS that we will see on the screen will be less

So shouldn’t I buy the RX 6400?

We must be clear that this graphics card is a solution designed for simple configurations. It is designed for those who play casually and the amount of FPS is completely the same. Users who want to disconnect after work playing a game of any game. We will be able to move any game without problems, obviously, a God of War will cost more than a Fortnite or CS: GO.

We have to be aware that it is a graphics card that has a price of about €200, so we do not ask it to play 4K @ 60 FPS games either, since it is not designed for that. Simply, we must know that with the PCIe 3.0 interface it will have a worse performance in some games than if we install it in a system with PCIe 4.0.

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