Ugreen CM642 SSD enclosure review: Fast, roll-your-own USB4 storage

At a glanceExpert's Rating

Pros

Record-setting USB4 performance

Very affordable for the ilk

Handsome

Easy install of NVMe SSD

Cons

Cover screw isn’t captive

Our Verdict
Super fast, handsome, rugged, easy to use, and not all that expensive, Ugreen’s CM642 USB4 SSD enclosure is a great way to roll your own high-performance external storage.

Price When Reviewed
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The Ugreen CM642 is an affordable 40Gbps, USB4 enclosure that lets you use any form factor (2230 to 2280) or capacity NVMe SSD as fast external storage. It’s handsomely designed, and while not as fast as some pre-populated USB4 SSDs, still plenty fast.

Read on to learn more, and then check out our roundup of the best external drives for comparison.

What are the Ugreen CM642’s features?

The CM642 is svelte, if not diminutive at approximately 4.5-inches long, 1.75-inches wide, and 0.75-inches thick. The gun-metal gray enclosure with copper highlights is largely metal, and suitably hefty at a little less than 6 ounces. I say suitably to mean it doesn’t feel cheap or flimsy in the least. It’s not bad looking either. I like it.

A single small, non-captive (be careful) screw allows access to the 2230/2242/2260/2280, M.2/NVMe slot (below) on the inside.






Nicely, you can use just about any small screwdriver — the head of the screw isn’t micro like many. Nonetheless, Ugreen includes a small screwdriver along with Type-A to Type-C and Type-C to Type-C cables. Be sure to use these rather than older Type-C cables to ensure 40Gbps performance.

Ugreen includes a silicone sleeve (shown below) to protect the case from scratches and keep it from scratching other stuff. SSDs don’t need much help when it comes to shock resistance, but it’s a nice touch, and also keeps the drive from sliding around on slick surfaces.






Ugreen uses ASMedia’s ASM2464PD USB4 chip, which is now showing up in decent quantities, so that products like the CM642 should become more widely available. There’s a small, nearly noiseless fan to keep the chip and drive relatively cool.

How much does the Ugreen CM642 cost?

At the time of this writing, the CM642 is going for $110 on Amazon. You can get cheaper USB 3.2×2 enclosures that will deliver 20Gbps (roughly 2GBps) performance. Note, however, that unlike USB 3.2×2 which drops to 10Gbps on Mac Thunderbolt ports, USB4 is fully supported, so you’ll get the 40Gbps speeds on Apple’s products as well.

Adding an SSD to the mix will cost anywhere from $40 (256GB) to $650 (8TB), with the sweet spot being the 1TB ($60) to 2TB ($160) range. There’s absolutely no reason to go PCIe 5.0, or even PCIe 4.0 for that matter, though the latter is far more common than PCIe 3.0 these days. USB4 can’t use their extra bandwidth, and small-file performance won’t be any better than PCIe 3.0.

Otherwise, my standard NVMe M.2 SSD advice applies: Avoid QLC if you regularly write large amounts of data, get a DRAM design if you’re going to run an operating system off the drive or want top random performance, and stick with cheaper TLC HMB designs otherwise.

The Ugreen CM642 SSD is the fastest USB4 external drive we’ve tested.

How fast is the Ugreen CM642?

The good news is that the CM642 is the fastest unpopulated USB4 enclosure we’ve tested. Of course, it’s also the only unpopulated USB4 enclosure we’ve tested other than the cheaper, soon-to-be-reviewed Ugreen CM850 the company also sent us.

Better news? It’s also the fastest, albeit by a very small margin over the populated USB4 SSDs we’ve tested — the Adata SE920 and the OWC 1M2. Of course, I used the very fast 8TB version of WD’s SN850X inside, which no doubt gave the CM642 an advantage.




The CM642 did very well reading and writing CrystalDiskMark 8. Longer bars are better.

Random 4K performance under CrystalDiskMark 8 was also excellent. OWC and Lexar weren’t forthcoming about the chips inside their SSDs, but we’re guessing they’re also the ASMedia controllers.




There’s nothing not to like about the CM642’s random performance under CrystalDiskMark 8. Longer bars are better.

Note that you need to use a good 40Gbps cable with the CM642, such as those provided in the box. Hanging the CM642 off my other, older Type-C cables resulted in 10Gbps-like performance.

The 48GB transfers were also top-notch. Fastest ever for a USB4 SSD.






While not light years faster, shaving a couple seconds off the 450GB write time is still a win. Again, the CM642 was top dog in a very fast pack.




This is a decent 450GB write time, but actually slower than a couple of USB 3.2×2 20Gbps SSDs we’ve tested. Shorter bars are better.

The CM642 never suffered any thermal related issues, which actually puts it slightly up on its CM850 cousin (to be reviewed soon on Macworld) in that regard. The CM850 required removing its silicon sleeve to complete our 450GB write.

We of course have to take into account the SN850X’s superior performance when tallying the results, but even so, it’s obvious the CM642 is capable of top-notch speed. Not half bad for a little over $100.

Should you buy the Ugreen CM642?

If you already have a spare NVMe SSD, absolutely consider leveraging it as external storage via the CM642. If you’re planning to start afresh, you can still roll your own fast external storage using it for well under $200 and employ bargain SSDs for higher capacities at lower price points than already populated models. A great enclosure from Ugreen.

How we test

Drive tests currently utilize Windows 11, 64-bit running on an X790 (PCIe 4.0/5.0) motherboard/i5-12400 CPU combo with two Kingston Fury 32GB DDR5 4800MHz modules (64GB of memory total). Both 20Gbps USB and Thunderbolt 4 are integrated to the back panel and Intel CPU/GPU graphics are used. The 48GB transfer tests utilize an ImDisk RAM disk taking up 58GB of the 64GB of total memory. The 450GB file is transferred from a 2TB Samsung 990 Pro which also runs the OS.

Each test is performed on a newly NTFS-formatted and TRIM’d drive so the results are optimal. Note that in normal use, as a drive fills up, performance may decrease due to less NAND for secondary caching, as well as other factors. This can be less of a factor with the current crop of SSDs with far faster late-generation NAND.

Caveat: The performance numbers shown apply only to the drive we were shipped and to the capacity tested. SSD performance can and will vary by capacity due to more or fewer chips to shotgun reads/writes across and the amount of NAND available for secondary caching. Vendors also occasionally swap components. If you ever notice a large discrepancy between the performance you experience and that which we report, by all means, let us know.