Jarrod’s Tech created an interesting experiment to test the limits of connecting a Thunderbolt 4 laptop to an external GPU setup with Nvidia’s RTX 4090 FE card. Of course, no one expects an eGPU setup to perform at the same level as a desktop equivalent, but the test also reveals the obvious limitations of Intel’s high-end i9-12900HX mobile processor. Jarrod felt that the i7-1260P laptop might struggle in some cases, so he added the i9-12900HX model. Surprisingly, in some gaming scenarios, the i7-12600P turned out to be significantly faster.
Early testing reveals that a desktop PC with a PCIe 4.0 X16 connector has 10x the bandwidth compared to Thunderbolt 4 laptops. That gap should soon narrow significantly with the introduction of 80 Gbps Thunderbolt, and things may get even better with 120 Gbps mode, but until then, Thunderbolt 4 / USB4 doesn’t seem to be slowing down the RTX 4090.
As Jarrod presents the results of the first 10 game tests, it becomes clear that the i9-12900 HX is a problem with the Thunderbolt 4 connector, which lags behind the i7-1260P in quite a few cases. Not to mention, the RTX 3070 Ti laptop GPU paired with an i9 CPU by default is faster than the RTX 4090 eGPU at 1080p and 1440p. Seeing the pattern taking shape, Jarrod completely skipped the i9 tests for the rest of the game scenarios
In some games, like Red Dead Redemption 2, the laptops showed the same number of FPS at all resolutions, which means something of a bottleneck. Not only do the tests highlight how limited the Thunderbolt 4 connection is when it comes to GPUs being able to take advantage of high bandwidth, they also show that the limits often result in excruciating stuttering at FPS numbers below 301%.
The limited bandwidth of Thunderbolt 4 is believed to be caused by the scalable BAR feature. However, Jarrod was unable to test this as there is no way to turn it off on laptops. The video comments also provide an explanation as to why the i9 is slower: apparently the i7-1260P has a built-in TB4 controller, while the i9-12900HX laptop has a Maple Ridge TB4 controller on its motherboard.
Since we now have AMD laptops and mini PCs with USB4 connections, it might be nice to see Team Red’s implementation on par with Intel.
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I first entered the wonderful world of IT&C when I was about seven years old. I was instantly fascinated by computer graphics, whether it was from games or from 3D programs like 3D Max. I am also an avid sci-fi reader, astrophysics buff, and cryptocurrency enthusiast. in 2006 I started writing PC related articles for Softpedia and several blogs. I joined the Notebookcheck team in 2017. over the summer and am currently a senior technology writer covering CPU, GPU and laptop news.