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

Published: Mar 5th 2023, 12:54 GMT   Comments

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

TechPowerUP has a new edition of their PCIe scaling test featuring 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 it offers higher speeds and greater bandwidth than its predecessors. The “x16” and “x8” refer to the number of data lanes that a particular PCIe slot has.

Thus 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 a 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.

Exactly this was demonstrated by TechPowerUP who updated their PCIe scaling review with the newer hardware. Instead of the Ryzen 7000 system they used months ago, it was based on Intel Core i9-13900K CPU instead. This system is now used for their GPU testing.

Furthermore, TPU took the feedback from the community to include newer titles with raytracing enabled, to ensure that bandwidth utilization is at the highest possible level.

NVIDIA GeForce RTX 4090 PCIe Scaling Test, Source: TechPowerUP

The results are just as expected, showing a small difference between Gen4 x16 and x8 modes. The latter is also equivalent to the x16 lane on PCIe Gen3, so this shows that even on an older version of the standard, gamers should still not expect a major performance loss.

TPU’s game selection has been updated with newer titles, such as Elden Ring or Far Cry 6. Those gamers have shown the most visible differences between the x16/x8 modes, going up to 8.3%:

NVIDIA GeForce RTX 4090 PCIe Scaling Test, Source: TechPowerUP

Performance loss is more significant for x4 mode, lowering the performance by 6% to 7%. Yet, the biggest impact should be expected from x4 mode, which is an equivalent to Thunderbolt 80 Gbps port used by external GPUs. Here gamers should expect 17% to 21% performance loss.

The PCIe standard may indeed have an impact on performance, but it is more likely to be seen on mobile graphics with lanes being limited from 8 to 4, rather than desktop GPUs losing half of the lanes. Exactly this scenario is tested in this review based on Z790 motherboard, which would sacrifice half of the available CPU PCIe lanes (in this case Gen5) for NVMe storage.

Source: TechPowerUP

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