by As one of PC Gamer’s hardware writers and reviewers, I handle a lot of different PC parts. But there’s one part in particular that gets me excited every time I use one. I am referring to M.2 SSDs. In fact, I hate them. They have so many unnecessary drawbacks. I’ll admit that the form factor is well suited for laptops, but for a desktop computer? It’s not.
What’s really frustrating is that there is a man-made alternative that has all the advantages of M.2, and essentially none of the disadvantages. It’s called U.2 (With U.3 waiting in the wings). Sadly, despite fleet inclusion on some boards a few generations ago, U.2 never caught on in the consumer space. And I want it back.
When the first SSDs were launched, it was clear that the aging SATA and mSATA interfaces were insufficient to handle the increased speeds of these new flash drives. A new standard was needed. NVM Express was developed specifically for non-volatile memory (NVM), but NVMe is not a connector, it is a specification or protocol. NVMe devices come in different form factors with different connections. These include PCI Express add-in cards or have SATA Express, M.2, or U.2 connectors.
SATA Express never caught on. Some high-end Intel Z97 and X99 motherboards came with SATA Express ports but I didn’t test one and all support disappeared after a short while.
U.2—my hero—appeared briefly on some high-end consumer motherboards a few years ago, but was always more of an enterprise-oriented solution. It lives on, and many workstation motherboards still include U.2 ports.
elevation M.2
For some profitable reason, someone decided that the best way forward was to attach an SSD directly to the motherboard. M.2 quickly became the most widely adopted connection and to this day, almost every performance-based consumer SSD is a 2280 NVMe M.2 form factor drive.
So why do I think M.2 SSDs attract? Where do I start? A typical 2280 size drive is too small, both physically and in capacity. They run hot and prone to throttling. They often sit right next to (if not below) a heat-dumping graphics card. Coincidentally, this week I reviewed the Teamgroup Siren Duo360 AIO cooler which also comes with an integrated SSD water block. Unfortunately, it highlights a growing problem with SSDs. The fact that PCIe 5.0 SSDs require chunky heatsinks mounted on the motherboard is a sad situation, not to mention water cooling.
PCIe 4.0 and especially PCIe 5.0 M.2 slots add complexity to motherboards making them more expensive. They take up a lot of PCB space. They are difficult and fiddly to install, sometimes require removing the GPU and removing half a dozen tiny screws – which I loose too often and lose to the seventh circle of hell case. Then you have to put it all back together, and hopefully a weak, flimsy or crumbling thermal pad aligns and the drive is firmly fitted in the M.2 slot. There are a few reasons to start.
Why U.2 rocks
U.2 drives eliminate all these problems while retaining all the advantages. A U.2 drive can be considered more or less a modern 2.5-inch SATA drive with support for an NVMe PCIe connection. In my opinion they are better than M.2 drives in basically every way. Here’s why:
A U.2 drive can be isolated from other heat generating components, especially the graphics card. A physically separated drive is easier to cool. Most PC cases hold 2.5-inch or 3.5-inch drive bays, and putting three or four U.2 drives into a space cooled by 120mm intake fans will keep them cool at all times. This will prevent them from rotting, which will lead to a longer life and thus keep your data safer. The last point can often be ignored.
A 2.5-inch form factor drive can easily incorporate a large heatsink, either internally or as part of the drive housing (as seen in the example above). In addition, SSD manufacturers are not restricted by the M.2 2280 form factor PCB. That means more PCB space is available for larger dies and larger capacities, or physically larger controllers with heat dissipation properties improved. They could even use cheaper manufacturing nodes.
Your next machine
Best gaming computer: The top pre-built machines from the pros
Best gaming laptop: Notebooks perfect for mobile gaming
And of course, getting rid of a bunch of M.2 slots FreeS up the motherboard PCB space and getting rid of the need to cover half the motherboard with metal slabs to keep the drives cool.
It’s easier to send signals from hardened connectors rather than having electrically sensitive traces running all the way across the motherboard. I’m sure a motherboard with one M.2 slot and four stacked U.2 ports would be cheaper to manufacture. Is it any wonder that a high-end motherboard can cost well over $500?
A lesser known fact is that U.2 drives use 12V power, whereas M.2 only uses 3.3V. There is some industry momentum towards moving PCs to 12V only designs. Intel released the ATX12VO standard in 2019 but did not adopt it. A single 12V computer is more efficient, simpler in design, and hopefully cheaper to make. There is another point in favor of U.2.
Do I care about seeing an inch of cable sticking out the side of my motherboard before it disappears through a hole and out of sight? No. Any. A bit.
U.2 2.5-inch SSD is easy to install and is swappable. It can be installed in one of a million cases with 2.5-inch drive bays without tools. Plug the cable and power connector in and you are good to go. Some tiny systems might be at a disadvantage, but it’s not like a 2.5-inch drive bay or three requires a monster case. Only the smallest NUC type systems would be at a disadvantage, and would most likely use custom motherboards and may still include M.2 slots anyway.
Are there any disadvantages to using U.2 over M.2? Well, you need to use a cable to connect them. Some would say that M.2 drives are a more elegant solution. No cables means a cleaner build. But I don’t care about seeing an inch of cable sticking out the side of my motherboard before it goes through a hole and out of sight? No. Any. A bit. Someone could make a U.2 RGB cable.
Oh, I can’t believe I went there.
Sorry, but I just can’t fall in love with M.2 SSDs. They are small, fiddly, hot, harder to install, add cost and complexity to motherboards and are limited in capacity. U.2 addresses all these weaknesses at the cost of requiring slightly more case space and using cables. Enough. Those are trade-offs I’m happy to accept.
Clearly driving U.2 has an edge. Give me the choice and I will follow. But, no matter what happens, with or without you, the insatiable desire for fast flash storage will not go away. I hope the future is not all M.2 lemon drive. If U.2 comes back, it will be a beautiful day.
