Should I Prioritize GPU x16 or Two Full-Speed PCIe 5.0 SSDs?
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MellowCedar42
I'm planning an X870E build with a graphics card and two PCIe 5.0 x4 NVMe SSDs. Depending on the motherboard and which M.2 slots are used, I can either run the GPU at PCIe 5.0 x8 while both SSDs operate at x4, or keep the GPU at x16 while the second SSD drops to x2. The boards I'm comparing include the ASUS ROG Strix X870E Gaming WiFi, ASUS ROG Strix X870E Gaming WiFi 7 Neo, and Gigabyte X870E Aorus Elite X3D.
My understanding is that a current GPU usually loses only a small amount of gaming performance when moving from x16 to x8, although much of the information I've seen concerns PCIe 4.0. I also believe PCIe 5.0 x2 offers roughly the bandwidth of PCIe 4.0 x4. For a typical gaming and general-use system, would it make more sense to prioritize the GPU's full x16 connection or keep both NVMe drives at PCIe 5.0 x4?
Answers
Check the lane diagram for each exact motherboard rather than assuming every X870E board behaves the same way. Some boards connect the second CPU-attached M.2 slot in a way that reduces the GPU slot to x8, while others keep the GPU at x16 and reduce that M.2 slot to x2. Chipset-connected M.2 slots may avoid affecting the GPU, but they can have their own bandwidth limitations.
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PCIe 5.0 x8 provides about the same bandwidth as PCIe 4.0 x16, so dropping the GPU to x8 should have very little effect on gaming performance with current graphics cards. Likewise, PCIe 5.0 x2 is roughly equivalent to PCIe 4.0 x4 for sequential bandwidth. The bigger question is whether your workloads can actually use two PCIe 5.0 SSDs at those speeds; most gaming and everyday tasks cannot.
MellowCedar42: The two-drive setup is mostly for organization: I like keeping the operating system and applications separate from my games and media. Since PCIe 4.0 and 5.0 drives are similarly priced, I was leaning toward PCIe 5.0, but I’m realizing my normal usage probably won’t benefit much from the extra bandwidth.
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You may not need an X870E board for this setup. A well-designed B850 board can offer three M.2 slots without taking lanes away from the GPU, depending on the model. Also, for an operating-system drive, game drive, and media storage, a good PCIe 4.0 SSD is usually already more than fast enough. I’d prioritize the motherboard’s lane layout, thermals, and features over the headline PCIe 5.0 speed.
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MellowCedar42: That’s the distinction I was running into. With one drive installed there’s no issue, but adding a second drive to a CPU-direct M.2 slot changes the GPU or SSD link depending on the board.