This Specification Change Could Prevent You From Upgrading To A PCIe 5 SSD
If you're familiar with M.2 SSDs, then you know that the standard sizes are named "M.2-2280", "M.2-2230", and so on. The last half of the number refers to the length of a drive's PCB, so an "M.2-2280" SSD is 80 millimeters long. M.2 SSDs officially can be up to 110mm in length, or as short as 30mm.
The first half of the number is the width, 22mm. To date, virtually all consumer M.2 SSDs have been 22 millimeters in width, and this size has been taken into account in myriad motherboard, mini-PC, and laptop designs. A wider drive simply won't fit in the space allotted for many M.2 slots.
Image: PCI-SIG, via TechPowerUp
Well it turns out that PCI-SIG, the consortium that manages such things, actually ratified a standard for M.2 SSDs with a 25-mm width back in 2020. As TechPowerUp points out, this information comes to light by way of some leaked specifications for Gigabyte X670 motherboards that list support for "M.2-25110" SSDs.
As for why the wider form factor is coming, it may be down to the need for slightly more space for PCIe 5.0 signal routing. Having a bit more room to separate traces can be a boon when you're trying to reduce crosstalk and noise, which are both major concerns for devices operating at the kinds of signal rates that PCIe 5.0 allows. While PCIe has retained the same frequency stability spec from 1.0 to 4.0, PCIe 5.0 tightens that spec by 66%, and many other screws have been tightened to make sure signals stay intact, too.
It's also possible that the extra space could help cooling ever-so-slightly. As we reported before, Phison's CTO Sebastien Jean noted that PCIe Gen5 SSDs will be power-thirsty enough that many devices could come with or even require active cooling. That's a wild thought considering the minuscule size of M.2 SSDs, but it makes sense in light of the potential power draw of upcoming PCIe 5.0 SSDs.
Of course, if you don't have a PCIe 5.0-capable system, there's little lost here. It's also true that the connector doesn't appear to have changed, so it's likely that many extant Alder Lake systems—the only ones with PCIe 5.0 support, for now—have space to hook up a brand-new PCIe 5.0 M.2 SSD, anyway. Here's hoping all of the upcoming PCIe 5.0 hardware takes the wider form factor into account.