The tech specs say that the laptop supports USB4. But, from Wikipedia:

USB4 by itself does not provide any generic data transfer mechanism or device classes like USB 3.x, but serves mostly as a way to tunnel other protocols like USB 3.2, DisplayPort, and optionally PCIe.

The 13" M2 spec, https://support.apple.com/kb/SP870?locale=en_US, says it supports "USB 3.1 Gen 2 (up to 10Gb/s)". But, the 16" M2 spec, https://support.apple.com/kb/SP890?locale=en_US, is silent on that; all it says is USB4.

Does anyone know? I'm preparing to order an external SSD and I'd rather not spend more for USB 3.2 Gen 2x2 if it won't be utilized.

svenmany said:

The tech specs say that the laptop supports USB4. But, from Wikipedia:

The 13" M2 spec, https://support.apple.com/kb/SP870?locale=en_US, says it supports "USB 3.1 Gen 2 (up to 10Gb/s)". But, the 16" M2 spec, https://support.apple.com/kb/SP890?locale=en_US, is silent on that; all it says is USB4.

Does anyone know? I'm preparing to order an external SSD and I'd rather not spend more for USB 3.2 Gen 2x2 if it won't be utilized.

Click to expand...

By definition, USB specs are supposed to be backwards compatible. Looking at the most recent update to the USB 4.0 specification (from October 2022), I can't tell for sure what the status is of Gen 2 2x2, although Gen 2 in its initial spec is supported.

dmccloud said:

By definition, USB specs are supposed to be backwards compatible. Looking at the most recent update to the USB 4.0 specification (from October 2022), I can't tell for sure what the status is of Gen 2 2x2, although Gen 2 in its initial spec is supported.

Thanks for that.

I've spent some time on https://en.wikipedia.org/wiki/USB4. There are a couple of charts. One chart says that USB 3.2 Gen 2x2 is a supported transfer mode. I might be misreading it somehow. Even if that mode is supported, it could be that the recent M2 Macs don't use that mode.

The M1 MacBook Pro's supported USB4, but they did not support the 2x2 mode. Which meant their USB speeds topped out at 10 Gb/s. The 2x2 mode tops out at 20 Gb/s.

I just got off the phone with a senior technical advisor at Apple. He is going to research this question for me via internal channels. He'll get back to me this coming Wednesday with the results.

2x2 was an optional feature, and Apple refused to waste time implementing it, for better or worse. Some considers 2x2 a half measure only for temporary solutions.

And even though I haven't seen an explicit test, but seeing some speed test of generic type-C SSDs being plugged to M2 Macs I have not seen anyone reporting better than 10Gbps speed for the last weeks. So not a confirmation but that is that.

Chancha said:

2x2 was an optional feature, and Apple refused to waste time implementing it, for better or worse. Some considers 2x2 a half measure only for temporary solutions.

And even though I haven't seen an explicit test, but seeing some speed test of generic type-C SSDs being plugged to M2 Macs I have not seen anyone reporting better than 10Gbps speed for the last weeks. So not a confirmation but that is that.

Thanks for that info. I guess the full measure would be for me to buy a thunderbolt external SSD, but they are very expensive.

I was either going to buy a SanDisk Gen 2x2 drive or a slower SanDisk Gen 2 drive. For the second one, I'd only get 10 Gb/s, even if the mac supports 2x2. But, the first one would be a waste of the extra money if the mac doesn't support 2x2.

I'll certainly report it here if Apple gets back to me with more information.

Got a call back from Apple support today. He doesn't know. The advisor put the question out to just one person and never got an answer. All the advisor was able to say was the it supports USB4 to 40 Gb/s.

USB4 supports various transfer mode. There's a great table of them at https://en.wikipedia.org/wiki/USB4. The Mac's 40 Gb/s is probably is USB4 Gen 3x2. And it might very well support 20 Gb/s, but it might do so with modes that don't match USB 3.2 Gen 2x2 specs (encoding and lane count).

I'm giving up waiting on an answer and going to make the assumption that 3.2 Gen 2x2 is not supported. I'm buying the cheaper drive.

Supported or not Apple Silicon USB transfer speeds just aren't that great. Apple likes Thunderbolt, which works great....other than all the Thunderbolt devices out there are unreasonably expensive.

dmccloud said:

By definition, USB specs are supposed to be backwards compatible. Looking at the most recent update to the USB 4.0 specification (from October 2022), I can't tell for sure what the status is of Gen 2 2x2, although Gen 2 in its initial spec is supported.

I think 3.2 Gen 2×2 (20 Gbit/s) is optional in the USB 4 spec. Although 3.2 2x1 (10 Gbit/s) is supported.

SpotOnT said:

Supported or not Apple Silicon USB transfer speeds just aren't that great. Apple likes Thunderbolt, which works great....other than all the Thunderbolt devices out there are unreasonably expensive.

The cheapest way I found to get 40 Gb/s (signaling rate - data plus overhead) is by using an M.2 enclosure. I found one solution; the enclosure company advertises that, when paired with Samsung's 980 PRO SSD, it gets over 2500 MB/s. I priced it at around $290 for 2 TB. That's a bit expensive for me for my needs. I'll probably go that way one day for my "really active" files when my internal 2 TB drive's gets close to full.

svenmany said:

The cheapest way I found to get 40 Gb/s (signaling rate - data plus overhead) is by using an M.2 enclosure. I found one solution; the enclosure company advertises that, when paired with Samsung's 980 PRO SSD, it gets over 2500 MB/s. I priced it at around $290 for 2 TB. That's a bit expensive for me for my needs. I'll probably go that way one day for my "really active" files when my internal 2 TB drive's gets close to full.

Might want to update your firmware ASAP.

steve62388 said:

Might want to update your firmware ASAP.

Samsung Issues Fix for Dying 980 Pro SSDs

Download the firmware fix ASAP if your 980 Pro is affected

www.tomshardware.com

As it happens, I do have 980 Pro's in my Windows machine. I updated them this morning. Thanks for the heads up though.