GeForce RTX 4090 and Core i9-13900K PCIe scaling test shows 2% difference between x16 and x8 mode

TPU’s updated PCI Express scaling test with new games and the Intel platform

TechPowerUP has a new edition of its PCIe scaling test with Intel Core i9-13900K processor and RTX 4090 GPU.

NVIDIA GeForce RTX 4090 Founders Edition, Source: TechSpot

PCI Express (PCIe) is a standard interface for connecting devices inside a computer. PCIe Gen4 is the fourth generation of this standard and offers higher speeds and greater bandwidth than its predecessors. “x16” and “x8” refer to the number of data lanes that a given PCIe slot has.

So far, only one company has released a PCIe Gen5-compatible GPU: Chinese brand Moore Threads. Neither AMD nor Intel and NVIDIA are rushing into this standard, probably for good reason.

A PCIe Gen4 x16 slot has 16 data lanes, while a PCIe Gen4 x8 slot has 8 data lanes. The difference in the number of lanes means that x16 slots can provide twice the bandwidth of x8 slots. That’s the theory, in reality it may not always show such a difference in actual gaming tests.

This is exactly what was demonstrated by TechPowerUP, who updated their PCIe scaling test with the newer hardware. Instead of the Ryzen 7000 system used months ago, it was instead based on an Intel Core i9-13900K CPU. This system is now used for their GPU tests.

Additionally, TPU has taken community feedback into account to include newer titles with ray tracing enabled to ensure bandwidth usage is at the highest possible level.

NVIDIA GeForce RTX 4090 PCIe Scaling Test, Source: TechPowerUP

Results are as expected, showing a small difference between Gen4 x16 and x8 modes. The latter also corresponds to the x16 lane on PCIe Gen3, which shows that gamers should not expect a large drop in performance even on an older version of the standard.

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TPU’s game selection has been updated with newer titles like Elden Ring or Far Cry 6. These players have shown the most visible differences between x16/x8 modes, increasing up to 8.3%:

NVIDIA GeForce RTX 4090 PCIe Scaling Test, Source: TechPowerUP

The performance loss is more significant in x4 mode, lowering performance by 6% to 7%. However, the biggest impact is expected from the x4 mode, which corresponds to the Thunderbolt 80 Gbps port used by external GPUs. Gamers have to reckon with a performance loss of 17% to 21% here.

The PCIe standard can actually impact performance, but it’s more likely to be seen in mobile graphics, where lanes are capped from 8 to 4, than desktop GPUs losing half the lanes. Exactly this scenario is tested in this test based on the Z790 motherboard, which would sacrifice half of the available CPU PCIe lanes (in this case Gen5) for NVMe storage.

Source: TechPowerUP