While PCIe 5.0 has technically been a thing since 2021, there haven't been any PCIe 5.0 devices to buy for a while. However, earlier this year, we finally saw the release of the very first PCIe 5.0 SSDs for the M.2 form factor, which promised speeds of over 10,000MB/s — the first time the mainstream storage medium has ever seen five-digit MB/s speeds, instantly making them some of the best SSDs around. We can probably expect later PCIe 5.0 SSDs to hit almost 16,000MB/s, which is the PCIe 5.0 interface's peak.
However, all that performance comes at a cost, not simply a monetary cost but a thermal cost. These SSDs consume so much power and create so much heat that without serious improvements, they may never see the kind of mass adoption PCIe 4.0 achieved. PCIe 5.0 SSDs might have a big problem on their hands, one that currently prevents them from being as universal as their PCIe 4.0 predecessors.
PCIe 5.0 SSDs are getting really hot
The story started in May when the first reviews of these PCIe 5.0 SSDs started popping up. It was Corsair's MP700 that raised concerns the most, as this drive launched without a heatsink, even though early versions included one. TechPowerUp saw its test system crash when its MP700 got too hot, while Phoronix's test bench experienced tons of errors in just three minutes.
The thing is, PCIe 5.0 SSDs right now are just really hot without exception. Almost every other company is pairing its PCIe 5.0 SSDs with heatsinks to combat the heat per a recommendation from Phison, which makes controllers for PCIe 5.0 SSDs. Phison even recommends that PCIe 5.0 SSDs are placed with not just a heatsink but an active cooler like a fan, too. These are totally unprecedented measures for keeping a mainstream SSD cool, as the power consumption is far higher than ever before.
The thing is, PCIe 5.0 SSDs right now are just really hot without exception.
In our own review of Crucial's T700, which uses the Phison controller present in the MP700, the SSD hit 81 degrees Celsius with a motherboard heatsink installed. Granted, the drive was tested in a pretty warm environment (not that it would invalidate the testing), but the motherboard's M.2 heatsink was absolutely massive and was designed to be overkill. Similarly, I observed my sample of MSI's Spatium M570 (which does come with its own heatsink) to also hit 81 degrees Celsius, but my testing environment was significantly cooler.
Of course, we saw something similar with the first PCIe 4.0 drives, too. Many of these first-generation models also came with heatsinks, but the best PCIe 4.0 SSDs, like Samsung's 990 Pro, don't even require a heatsink for good performance. It is true that high-end drives like the 990 Pro slow down a tad when running long and intensive workloads without a heatsink, but that's nothing like shutting down from overheating.
While it's impossible to rule out that Phison and other companies may be able to create more efficient controllers and NAND, we know it's probably not coming any time soon since Phison's latest SSD, which hits up to 14,000MB/s, uses a fairly exotic cooling method that implies active cooling will still be required.
The consequences of failing to beat the heat
If it's just not possible to deliver speeds in the five digits without good cooling, that's a big deal for consumer electronics. It means that pretty much every PCIe 5.0 SSD will probably need to come with its own heatsink and shouldn't rely on motherboards to have one that's good enough. The T700 is proof enough that passive cooling, even on a big heatsink, isn't sufficient; you're probably going to need active cooling or a cool ambient temperature. This could range from mildly inconvenient to very annoying, especially since tiny fans tend to be whiny.
In the above image, you can see how I've compared the size of MSI's Spatium M570 to the Samsung 990 Pro. This SSD is as tall as the 990 Pro is wide, and it's even as tall as my ROG Zephyrus G14 is thick. There's absolutely no chance the M570 will fit in any remotely thin laptop, or any laptop that isn't specifically designed to accommodate it. That's the reality for pretty much any PCIe 5.0 SSD: there simply won't be room for one in a laptop that's not two centimeters or more thick. In the best-case scenario, laptops would have to be specially designed to cool PCIe 5.0 drives.
Without more efficient PCIe 5.0 SSDs, this performance will have to be limited to desktops and very thick laptops, which would be a shame for laptop users chasing the best performance. Laptops are increasingly becoming an appealing alternative to desktops thanks to modern designs that can get the most out of the latest hardware, but PCIe 5.0 SSDs pose a unique challenge. Though, there is time before PCIe 5.0 hits mobile devices, and that might be enough time to sort out the current issues with PCIe 5.0 drives.
On the other hand, maybe we won't care too much about PCIe 5.0 SSDs
While it's definitely bad if the industry can't figure out how to offer PCIe 5.0 SSDs without large and expensive cooling solutions, it might not actually be all that bad. If you look at benchmarks, the PCIe 5.0 interface is really only useful in sequential workloads with high queue depths and block sizes like simple file transfers. The reality is that lower queue depth, a lower block size, and random workloads are also quite common, especially for day-to-day tasks and games. Do we really need up to 16,000MB/s in most devices?
It definitely wouldn't be great if PCIe 5.0 can't get cool enough to be as mainstream as PCIe 4.0, especially since that implies future generations of PCIe would be similarly too hot. However, I don't think it would be a showstopper, either. A lot of PCIe 4.0 SSDs are barely any faster than older PCIe 3.0 drives in the kinds of workloads I talked about earlier, such as Samsung's 990 Pro versus its older 970 EVO Plus. We'll just have to see how things pan out, but for the foreseeable future, it looks like PCIe 5.0 SSDs is off to a hot, slow start.