I've noticed that many motherboards offer 4 or more M.2 slots supporting PCIe 5.0 or 4.0, but when it comes to PCIe slots, there are usually only 3, and often only one or two of them are practical. The primary slot is typically for GPUs (PCIe 5.0 16x), but the middle slot seems to be just PCIe 3.0 1x, and the third one is usually PCIe 4.0 4x, which doesn't provide much use besides extra USB ports. Is there any way to use an M.2 slot as a PCIe slot, and would it fit into the PCIe brackets of the case?
3 Answers
It's all about lane allocation and chipset capabilities. Motherboards often have more M.2 slots because most users are more concerned about high-speed NVMe storage than needing multiple GPUs. The lower slots typically run off the chipset and can be limited in lane availability. The marketing makes it look like there are more options, but really, the motherboard's design and CPU lanes dictate how much you can actually use.
The number of PCIe lanes is dictated by your CPU as well as the motherboard. Many users may only need one or two high-speed slots for things like NVMe storage or a capture card. It's about having flexibility—some folks might want multiple sound cards or networking cards, and the design caters to these varying needs.
Storage is the primary concern after GPUs in many setups, which is why more M.2 slots are provided. Most other components can function on onboard options, which are sufficient for average usage. But if you're looking for more diverse uses for PCIe slots, such as adding faster networking capabilities or additional cards, then that's a valid point!
I’m in a similar boat! I’m using the third slot for a capture card, and I'm considering adding things like Thunderbolt networking. It would definitely make more sense if there was a second PCIe slot that had more lanes available.