Recently, the TechPowerUP site has a series Testing the new PCIe scale have done that GeForce RTX 4090 graphics card and Core i9 13900K processor were present in it. The PCI Express (PCIe) interface is a standard interface used to connect internal components to a computer. Currently, the fourth generation of this interface called PCIe 4.0 is the most common generation and offers more speed and bandwidth than its previous generation. The terms x8 and x16 in the PCIe standard refer to the number of lanes that a PCIe slot can occupy.
Impact of PCIe interface on RTX 4090 performance
Until now, only one Chinese company called Moore Threads has introduced a graphics card compatible with PCIe 5.0 interface, and other big companies – Nvidia, Intel and AMD have not introduced any graphics card compatible with this standard, and for a good reason. for that they have
A PCIe 4.0 x16 slot can accommodate 16 lanes, and a PCIe 4.0 x8 slot can accommodate only 8 lanes. These routes are like highway lanes, and with this account, the bandwidth of the x16 slot is twice that of the x8 slot. But this difference is not necessarily linearly related to the final performance, and in fact, x8 and x16 slots are not 100% different in gaming.
This is exactly what TechPowerUP investigated in testing the RTX 4090 graphics card on PCIe x8 and PCIe x16 slots. Until a few months ago, Ryzen 7000 processors were used as the TechPowerUP graphics card testing platform, but in this test, the Core i9 13900K processor was used, and therefore, this platform will be used as the graphics card testing platform by the TechPowerUP team.
In addition, TPU has added newer games to the test and also tested the Ray Tracing feature at the request of users. Having RT enabled ensures that the highest possible bandwidth requirements are met.
The results, as we expected, show a small difference between the two PCIe x16 and PCIe x8 interfaces – something like 2 percent. The PCIe Gen4 x8 interface is functionally the same as the PCIe Gen3 x16 interface. Therefore, gamers who have older motherboards that do not support the PCIe 4.0 interface do not need to worry too much and are not going to lose much performance in terms of gaming.
The biggest drop is for the PCIe x4 interface
Things get worse when the PCIe 4.0 x4 interface is involved, with a 6-7% performance drop. However, the biggest performance drop is when the PCIe 4.0 x4 slot is used for new generation graphics cards. The bandwidth of these slots is the same as Thunderbolt’s 80 Gbps ports; The same port used by external graphics cards. This is why desktop graphics cards lose 17 to 20 percent of their performance when used externally.
As you have seen, the PCIe standard has an effect on the final performance of the graphics card; But the peak of its effect is seen in the transition from 8 paths to 4 paths. The importance of this issue in laptops, whose paths are limited to 4 and 8, is more than in desktops. In desktops, we generally deal with x8 and x16 slots, the difference in performance is negligible.
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