How to Check What PCIe Link Speed Your NVMe SSD Is Running At

You bought a fast Gen4 or Gen5 SSD, but is it actually running at that speed? A drive can silently drop to a slower link if it is in the wrong slot, sharing lanes, or limited by BIOS settings. Checking the real, negotiated PCIe link speed takes a couple of minutes and can reveal easy performance you are leaving on the table. Here is how to do it and what the numbers mean.

Understand what “link speed” means

A PCIe link is described by a generation and a lane count, like “Gen4 x4.” Each generation roughly doubles bandwidth per lane: Gen3 is about 1 GB/s per lane, Gen4 about 2 GB/s, and Gen5 about 4 GB/s. An NVMe SSD normally wants an x4 link. If your drive negotiated only x2, or dropped a generation, its ceiling is cut in half.

Negotiated vs capable

Tools show both what the slot is capable of and what it currently negotiated. The negotiated value is the one that matters. A Gen4 drive in a Gen3 slot will report a Gen3 link, and that is expected, not a fault.

Three ways to check

Using a Windows utility

Most SSD vendor tools and general hardware-info apps have a field labelled something like “PCIe link speed” or “current link width.” Open it, select your NVMe drive, and read the current values. You want to see the generation your drive supports at x4. Run a quick benchmark too: a Gen4 x4 drive should post sequential reads in the 5,000-7,000 MB/s range; if you see ~1,800 MB/s, you are stuck on a Gen3 or narrower link.

Checking in BIOS

Many motherboards show the link status for each M.2 slot and even let you force a generation. This is useful when a flaky Gen5 link causes instability and you want to lock it to Gen4.

Common reasons a drive runs slow

Wrong M.2 slot or shared lanes

Boards often wire one M.2 slot to the CPU (full speed) and others through the chipset or shared with SATA/PCIe slots. Populating a secondary slot can drop the link to x2 or disable SATA ports. Check the manual’s block diagram and move the drive to the CPU-connected slot for full bandwidth.

BIOS set to a lower generation

Some boards default a slot to Gen3 for compatibility. Set the slot to Auto or the correct generation, save, and recheck.

CPU or platform limits

An older CPU may only offer Gen3 lanes even on a newer board, so a Gen4 drive tops out at Gen3. That is a hardware ceiling, not a misconfiguration.

Verify with a quick benchmark

Numbers in a system tool are useful, but a short benchmark confirms the drive is delivering the bandwidth its link allows. Run a sequential read/write test and compare against the expected ceiling for the negotiated link. A Gen3 x4 link tops out near 3,500 MB/s, Gen4 x4 near 7,000 MB/s, and Gen5 x4 well above 10,000 MB/s. If your numbers land near the tier below what you expect, revisit the slot and BIOS settings.

Match the benchmark to the link

If a Gen4 drive benchmarks around 1,800 MB/s, it almost certainly negotiated an x2 width, a classic symptom of a shared or chipset-limited slot. Moving it to the primary CPU-connected M.2 slot usually restores full x4 speed instantly.

FAQ

My Gen4 SSD shows a Gen3 link. Is it broken?

Usually not. Either the slot, CPU, or a BIOS setting is limiting it to Gen3. Move the drive to the CPU-connected M.2 slot, confirm the slot’s generation in BIOS, and verify your CPU supports Gen4. If all three are correct and it still links at Gen3, the platform simply may not offer Gen4 on that slot.

Does running at x2 instead of x4 hurt gaming?

For load times the effect is small because games rarely saturate even a Gen3 x4 link, but you paid for x4 bandwidth so it is worth fixing. Large file copies and content work benefit most from restoring the full x4 link.

Bottom line: Use an SSD or hardware-info utility (or your BIOS) to read the negotiated PCIe generation and lane width, and confirm it shows your drive’s rated generation at x4. If it is slower, move the drive to the CPU-connected M.2 slot and check the BIOS generation setting before assuming the drive is faulty.