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celaconacr t1_jdfioj0 wrote

Reply to comment by QuietGanache in The Framework Laptop 16 promises the “holy grail” of upgradable graphics. by SUPRVLLAN

Razer Core X and similar eGPUs seem to do ok. I have seen a RTX 3080 rated at about 20% slower than on a desktop. Slightly better if you don't have to return the graphics output back down the thunderbolt connection. A large amount of memory on the cards can certainly help with the bandwidth. I can't really see it being an issue for most graphics cards when heat will stop them first in a laptop.

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Svenskensmat t1_jdgwklj wrote

A desktop RTX 380 maxes out at around 16GB/s in bandwidth utilisation over PCIe. 32Gb/s is the equivalent of 4GB/s in bandwidth, so it’s not nearly enough.

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celaconacr t1_jdhs888 wrote

It doesn't particularly matter what it maxes out at if the utilisation over time is much lower. e.g. a spike loading a new texture set would potentially have to wait 4 cycles rather than 1 but if there isn't another texture set waiting to be loaded after it's a small hit on performance.

The main bottlenecks for modern graphics cards aren't usually the PCIe lanes. As I put performance tests show it's about a 20% hit on a desktop class card with current games. Before eGPUs existed similar tests were done with GPUs running on 4 and 8 lanes with similar results. The result will vary by game, texture volume and the cards memory. The more memory the card has the less it will use PCIe.

For the future Thunderbolt 5 will be 80Gb/s uni-directional or upto 120 bi-directional so it will be even less of an issue. PCIe 5 will be a similar increase but again is likely low utilisation over time.

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