I have a mobile RTX 4090 in my GE78HX 14VG MSI Titan laptop, and I'm noticing something odd. In GPU-Z, it shows the bus interface as PCIe X16 4.0 but is running at X8 4.0. Is this normal behavior for laptops? Can I do anything to make it run at X16 4.0, especially during rendering tests? Thanks for any insights!
2 Answers
It's actually pretty normal for laptops. Laptop CPUs have a limited number of PCIe lanes, which means they're shared with components like your NVMe SSD and other stuff. Unfortunately, you can't switch it to 16 lanes—it's just how laptops are designed. But don't worry, running at PCIe 4.0 with 8 lanes still gives you plenty of bandwidth for your GPU.
Are you sure the GPU is installed in the correct slot? Some laptops have multiple slots, one that runs at 8x and another that supports 16x. But since you mentioned it’s a mobile GPU, it’s likely fixed in place. Just double-check your UEFI settings and make sure the MUX switch is set to use the dedicated GPU only, then re-run your tests. The mobile 4090 is typically an x16 card, so this might help!
Yeah, keep in mind that with a laptop, you usually can't change the configuration like you would in a desktop.
I've never opened my laptop to check, so I'm a bit unsure about the slots.