Your SSD might be running at half speed How to unlock the speed you paid for

Your SSD might be running at half speed How to unlock the speed you paid for

Even if you buy one of the fastest SSDs, you may find it running slowly, and not necessarily because there's something wrong with the hardware itself. Often, the problem can be easily fixed on your end without jumping through too many hoops.

With NVMe SSDs, you may not even notice that you're not fully utilizing your drive's potential, so even if you have nothing to complain about, it's always worth checking.

Why your NVMe SSD might not be running at full speed

It might be fast, but is it the fastest it can possibly be?

Assuming your SSD is not the best it can be, what's the problem? I'd wager that it comes down to PCIe bandwidth, and that can hide a few different micro-problems.

Before we dig in, let's talk about link negotiation, which is a core technical concept for an NVMe SSD. When you boot your PC, the SSD communicates with the motherboard, determining the highest common speed both sides support.

If the mobo supports PCIe Gen 5, but the SSD is capped at PCIe Gen 4, the motherboard will take that as the maximum SSD speed it can offer. But the generation of PCIe is just one part of this puzzle; there's also lane width (x2, x4).

If your SSD runs below spec, chances are that there's a mismatch either in the PCIe generation or in lane usage, i.e., the SSD might be using fewer lanes than it needs to provide the maximum advertised speed. NVMe is fast because it typically uses four PCIe lanes, so scaling down to two will be a major downgrade. (There's a caveat, though: some drives opt for x2 on higher PCIe gens, so check your SSD.)

Bandwidth depends on both using the correct PCIe generation and the correct number of lanes. Both need to be done right, or you're looking at an underperforming drive.

Choosing the right M.2 slot for your NVMe SSD is important, too. Connecting directly to the CPU cuts latency and gives the SSD a priority connection, so to speak. A drive on chipset lanes can still be fast, but it needs to compete against other devices over the CPU and chipset link.

It's worth remembering that while your motherboard determines the number of M.2 slots, the PCIe generation, and the lane width you have available for your SSD, your CPU does too. This leaves more room for potential misalignment.

The most common causes of PCIe bandwidth throttling

Some are avoidable, but some can't be helped.

With all that background out of the way, what are the actual causes of all that behind-the-scenes disappointment?

Most commonly, you'll find that the SSD may have been installed in the wrong M.2 slot, for example, a Gen 4 SSD being installed in a Gen 3 slot. The SSD will still work just fine in that scenario, but it'll be half as fast, capped to the Gen 3 maximum.

Lane sharing is another big one, because mobos only have so many lanes to go around. On some boards, if you use a specific M.2 slot, your second PCIe x16 slot may be disabled. On older motherboards, you may shut off one of your SATA ports.

Similarly, M.2 bandwidth settings need to be set up correctly in the BIOS. If the slot configuration is set to x2 mode instead of the standard x4, you're bound to see a performance drop. And sometimes, just reseating your drive can fix faulty link negotiation.

Lastly, you may just have the wrong drive for your hardware. A PCIe Gen 5.0 SSD needs the latest CPU and motherboard combo to run at maximum speed.

How to check your current PCIe lane assignment and speed

Dig into where the problem really lies.

My favorite way (and the industry gold standard) to check all things related to SSDs isCrystalDiskInfo, a free tool.

Using CrystalDiskInfo, you can easily check whether your SSD is running on the correct PCIe spec. Just download the program, run it, and look at the "Transfer mode," and more precisely, the "Current mode" and the "Supported mode." The former is what you're using, and the latter is what you should be using. If there's a mismatch, you've found your culprit.

1. Open up HWiNFO64 (you don't need to install it) and uncheck "Sensors only" at startup.
2. In the left-hand tree, expand "Bus," then "PCI Bus."
3. You'll see lots of different entries. Look for CPU-related options, such as "AMD PCIe GPP Bridge." It might also be under "System Agent" on an Intel platform. If you find it under Intel PCH or AMD Promontory/Chipset, it means it's running on a slower connection.
4. If the drive is connected to the CPU, you'll find it nested within one of those entries near the top.

This simple check will tell you whether you should move your NVMe SSD elsewhere or not.

How to fix PCIe speed issues

There are a few ways to try.

Depending on the nature of the problem, you might either have to physically open up your PC and move the SSD, or you might have to make some tweaks in the BIOS.

Start by reseating the drive to get rid of potential pin contact issues. Simply remove it and slot it back in. But while you're there, make sure you're actually using the correct PCIe slot for your chosen SSD, and if not, switch to a different slot.

You want your best drive to go into the slot that gets priority lanes and supports the highest PCIe gen—this is usually the topmost slot, but it varies based on the motherboard. This may sometimes reduce the main PCIe x16 slot (often used by the GPU) to x8, which you don't want to happen, so do your research before you make changes.

Next, make changes to your BIOS/UEFI. The exact path to follow here will vary depending on the motherboard's manufacturer.

Look for settings related to M.2 link speed, PCIe slot link speed, and PCIe mode. If the link speed is set to auto, try to change it to the correct PCIe gen instead, and if the board's PCIe x4 mode is disabled, make sure you enable it. Keep in mind that this might disable some SATA ports.

Does the difference in speed really matter?

Just because you can't see the performance loss doesn't mean it's not there.

There are many reasons behindan underperforming SSD, such as filling it up to full or letting it overheat, but these hidden issues I described above can arguably be worse than those big,major SSD problems, because you might not even notice them.

There's a clear reason why I often tell people not to go for the top-shelf SSDs—at a certain point, you just won't notice much of a difference in day-to-day use, but you'll definitely notice when transferring files, editing videos, or doing something else that's fairly resource-heavy.