MyDigitalSSD is now shipping one of the first USB enclosures for M.2 NVMe SSDs. The new M2X enclosure is based on the JMicron JMS583 USB 3.1 Gen 2 to PCIe 3.1 x2 bridge chip. This bridge translates the SSD's NVMe storage protocol into standard USB Mass Storage protocol or USB Attached SCSI Protocol (UASP), allowing for a portable SSD with much higher performance than the majority of portable SSDs that use SATA SSDs internally, while also offering much broader compatibility than Thunderbolt enclosures and portable SSDs like the Samsung X5.

The MyDigitalSSD M2X is a DIY kit for assembling a portable SSD with the user's choice of M.2 NVMe SSD. (M.2 SATA drives and M.2 PCIe drives that use AHCI instead of NVMe are not supported, but there are already plenty of enclosures for the former.) The bottleneck for sequential transfers will be the 10Gbps USB 3.1 Gen 2 host interface, which allows for around 1GB/s throughput. The JMS583 bridge chip is backwards compatible with USB 2.0 and the M2X is supplied with USB Type-C and Type-A cables, so the M2X will be plug and play with basically everything out there.

On the other side of the bridge chip is a PCIe 3 x2 link, so there's little reason to put a high-end NVMe SSD inside the M2X instead of a cheaper two-lane SSD such as the MyDigitalSSD SBX or the Kingston A1000, both based on the Phison E8 controller. There's no mention of NVMe Host Memory Buffer (HMB) support in the JMS583 documentation so DRAMless NVMe SSDs like the Toshiba RC100 used in the M2X will tend to have much worse random access performance than with a direct PCIe or Thunderbolt connection to the host, even before taking into account the NVMe to USB translation overhead.

The MyDigitalSSD M2X is bus powered and includes a thermal pad to help conduct heat from the M.2 SSD to the aluminum case. There doesn't appear to be a similar pad for the JMS583 bridge chip, which is rated to consume 700mW under load so its 8mm package will likely be the hottest component inside the M2X. Since USB ports usually only deliver 4.5W total, this leaves about 3.8W for the SSD itself. Most NVMe SSDs stay well below this when limited to 1GB/s, but sustained sequential writes could push some drives beyond this and lead to trouble. It's not clear if the JMS583 supports putting NVMe drives into a lower-power active state so that they throttle themselves before drawing too much power.

The MyDigitalSSD M2X is now available from Amazon for $39.99 or through MyDigitalDiscount for $36.14.

The JMS583 bridge chip debuted at Computex earlier this year. At the same show, ASMedia introduced their competing ASM2363 USB 3.1 to PCIe 3 x2 bridge, but products based on the ASMedia bridge have not yet made it to market.

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  • Billy Tallis - Tuesday, September 18, 2018 - link

    I agree that the brand name isn't at all creative, but they're not Chinese. The company is based upstate New York.
  • Death666Angel - Tuesday, September 18, 2018 - link

    Looks like an interesting product. Several JSM583 based products available on ebay, now that I know what to search for. :D I like having external adapters to products I'm using inside my PCs, makes troubleshooting easier. I'll get a SATA and NVME one, since I doubt we'll be seeing a combined product. They are even price competitive with USB thumb sticks and much more performant I'd guess. Not as tiny though. :)
  • Death666Angel - Tuesday, September 18, 2018 - link

    And since you seem to be responding to post here, Billy: Can you query MyDigitalSSD on their plans for Europe? They aren't really available here in Germany (usually one seller per product, heavily overpriced). They seem to be a good brand with well priced offerings. I wouldn't mind having another option here for great mid to low end SSD stuff. :)
  • Mikewind Dale - Tuesday, September 18, 2018 - link

    Yes, finally! I have a laptop with only one M.2 slot and I've wanted to upgrade the NVMe SSD but I knew that cloning my drive would be difficult. Whenever I upgrade a SATA drive, I just connect the new drive to a USB enclosure, clone, and then swap the two SATA drives. Now I can finally do the same with my NMVe drive! Yay!
  • tokyojerry - Thursday, September 27, 2018 - link

    Interesting that NVMe is starting to be supporting over USB3.1 Gen2 in these compact external cases. But unless such a case supports TB3 (thunderbolt 3) rather then USB3.1, will it not be an effort in futility to insert an NVMe module versus just a SATA-based module?

    For myself, I purchased a WD (Blue) M.2 SATA SSD 2TB and want to get an appropriate case for it. Would something like this WavLink be the most appropriate case to achieve best performance? ( )
  • Sushi_Desires - Wednesday, December 25, 2019 - link

    Perhaps I am misunderstanding the issue, but if the limiting factor on data transfer speeds for these external NVMe drives is the bandwidth of the USB interface, what is stopping firms from writing a custom firmware that lets users plug in 2 or even 3 of the same connectors to the drive at once to roughly double or triple the bandwidth?
  • Barney4 - Thursday, June 18, 2020 - link

    You claim in this article - "(M.2 SATA drives and M.2 PCIe drives that use AHCI instead of NVMe are not supported, but there are already plenty of enclosures for the former."


    And I have been looking since before you wrote this!!

    You tell me where all these AHCI enclosures are????

    I have been looking for an AHCI external enclosure for about 3 or 4 years since I have 3 of these things.
    The only external enclosure I found that is available is over US$600 (which works out to be about $1000 where I live) for an enclosure which is a ridiculous price, even for a Thunderbolt 3 enclosure.
    I am waiting for Icy Dock to release it's new U2 to USB 3.1 gen 2 adapter (CP087) later this year so I can start to use them again.

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