If you've made any storage upgrades recently, you may have come across PCIe 5.0 SSDs. They're pretty fast, but right now, upgrading to them doesn't make a whole lot of sense. It's a lot more money for little benefit, and the major drawback of their power consumption and heat generated makes them difficult to actually use at full pelt. With the PCIe 6.0 specification being published by PCI-SIG, it's possible that it's going to run the exact same risk of being too hot to handle, or worryingly, even more so.

Of course, the PCIe standard isn't just for SSDs, and is used for all kinds of devices, including GPUs. These problems may not necessarily pertain to GPUs and other devices that have active cooling, but SSDs particularly appear to struggle.

Why PCIe 5.0 ran so hot

It's all about power draw

PCIe 5.0 offers read speeds of up to between 14,000 and 16,000 MB/s, an impressive high number over the 8,000 MB/s offered by the previous generation. Signals have to be further amplified by transceiver circuits to maintain integrity, and additional re-drivers and equalizers have to be used to prevent signal degradation. All of this draws more power, which in turn generates more heat.

This is also why heatsinks over the M.2 drives have become more common on premium motherboards. These help with heat dissipation, as the controllers themselves have to work significantly more to maintain the much higher speeds that the previous generation didn't have. Phison, one of the companies that makes the controllers for PCIe 5.0 SSDs, even told Tom's Hardware that a heatsink is required for SSDs that use its E26 controller, which is most PCIe 5.0 SSDs on the market.

"It is important to note that all E26 SSDs shipped without a heatsink are intended to be used with a heatsink. Most motherboards shipping with PCIe Gen5 enabled also include cooling specifically designed for Gen5 SSDs. We offer the “bare drive” option to allow customers to use their existing cooling products."

On top of all of that, even when the full speed isn't being utilized, the lane signalling for PCIe 5.0 SSDs still runs at the maximum 32GT/s transfer speeds and draws the power required to maintain it.

These are the major reasons that we've seen PCIe 5.0 SSDs run hot, and why we've seen some companies experiment with ways to try and cool them. From active heatsinks to M.2 slots on GPUs, there have been some unique ways to try and tackle this particular problem. There's no evidence that PCIe 6.0 will run any cooler, and in fact, there's some evidence to suggest that it might even run hotter.

PCIe 6.0 might have even worse problems

Architectural changes will likely require better cooling than before

Firstly, PCIe 6.0 ups the ante significantly, doubling the transfer speeds of PCIe 5.0 to 64 GT/s, with SSDs poised to offer up to 26,000 MB/s in sequential read speeds. One of the big changes with PCIe 6.0 is a switch to Pulse Amplitude Modulation (PAM) with four levels, also known as PAM4. Previously, PCIe used non-return-to-zero (NRZ), and PAM4 stacks more bits into each clock cycle. This is efficient for data throughput, but it's more susceptible to signal integrity issues as a result.

To counteract these signal integrity issues, the hardware will need to be stronger and more capable of maintaining integrity with more re-drivers and equalizers. This means more power draw and more heat, which builds on top of the existing problems of PCIe 5.0. PCIe 6.0 also introduces a lightweight Forward Error Correction scheme to mitigate the higher bit error rate that PAM4 inherently brings. While labeled “lightweight,” FEC still adds extra overhead in real-world implementations. It also raises power consumption in the controllers, which need to perform these error checks in real time.

All of this means that PCIe 6.0 will likely consume even more power in M.2 SSDs, which in turn will increase heat dissipation. That's why many motherboards are starting to pack heatsinks for those M.2 slots, and it would seem that those will be more necessary than ever with the next generation of SSDs.

As already stated, PCIe isn't just a specification for NVMe drives, but it's still used in them. Your PCIe 6.0 GPU (which is many years aware from being released) will fare significantly better than the storage drives of today or tomorrow. However, there's almost certainly going to be a thermal limit when it comes to those SSDs, and it's unclear how manufacturers will deal with them. Given that PCIe 5.0 SSDs with the E26 controller from Phison were said to "require" a heatsink, I can't imagine things will be much better with something even faster and more power hungry.