PCIe Compatibility Checker
Check PCIe compatibility between your GPU and motherboard. See which generation you actually get, and whether the card will be bandwidth limited.
How PCIe compatibility works
PCI Express is both forwards and backwards compatible. Any card works in any slot that is physically large enough — the link simply negotiates down to the lowest generation and the narrowest lane count of the two ends. A PCIe 5.0 card in a 3.0 slot runs at 3.0 speeds; it does not fail.
Bandwidth doubles each generation
Each generation roughly doubles per-lane throughput: about 1 GB/s per lane at 3.0, 2 GB/s at 4.0 and 4 GB/s at 5.0. A full x16 link is therefore roughly 16, 32 and 64 GB/s respectively. Note that generations 3 and later use 128b/130b encoding, where 1.0 and 2.0 used the less efficient 8b/10b — which is why 2.0 to 3.0 is more than a straight doubling.
Graphics cards barely notice
This surprises people: even halving a graphics card's bandwidth typically costs only a few percent of frame rate. Cards hold their working set in VRAM and use the bus far less than the numbers suggest. The exception is cards with narrow x8 interfaces and small VRAM buffers — when memory runs short, data crosses the bus constantly and the loss becomes large.
Watch for lane sharing
Consumer processors provide a limited number of lanes. Installing an M.2 drive in certain slots commonly drops the primary graphics slot from x16 to x8, or disables SATA ports. The motherboard manual's lane-sharing table is the only reliable source — the marketing page will not mention it.
Physical size versus electrical width
A slot that looks like x16 may be wired for only x4. Board makers do this for secondary slots so larger cards still fit. Check the specification rather than the slot's appearance, and note that a card longer than an open-ended slot cannot be seated at all.
Frequently asked questions
Will a PCIe 5.0 card work in a PCIe 4.0 slot?
Yes. The link negotiates down to 4.0 and everything works normally. For graphics cards the performance difference is typically within a couple of percent.
Does PCIe 3.0 bottleneck a modern graphics card?
Rarely and only slightly - usually 1-3% at x16. The exception is cards with an x8 interface and 8 GB of VRAM, where running out of memory forces constant bus traffic and the loss can reach 10% or more.
Why did my graphics slot drop to x8?
Almost always because an M.2 drive is installed in a slot that shares lanes with it. Moving the drive to a different M.2 slot usually restores x16 - the manual's lane table shows which.
Is PCIe 5.0 worth having?
Not today for gaming. No current graphics card saturates PCIe 4.0 x16. It matters for Gen5 storage and for professional cards, and it is useful future-proofing rather than a present-day benefit.