Crucial X10 SSD transfer speeds on Mac Studio

MartinR explained the gist of it.

My understanding is that USB4 defines three different and incompatible "up to 20 Gbps" USB transfer modes.

• Two are new to USB4. One has the marketing name "USB4 20 Gbps" and it is mandatory for USB4 host ports. (Apple doesn't mention this mode explicitly in their Technical Specifications, but support is implied.)
• The third is USB 3.2 Gen 2x2. It is optional for USB4 host ports.

Essentially, the USB Implementer's Forum made it easy to throw USB 3.2 Gen 2x2 under the bus.

Aldervai wrote:

Although even if there is a ridculous apple thing where the USB 3.1 port is in action, instead of the USB 4

USB-C is a connector – and standards for allowing various other protocols to live on that connector. Your Mac Studio's USB4 / Thunderbolt ports are like "Swiss Army knives" that have multiple "blades":

• Thunderbolt 4 (up to 40 Gb/s)
• DisplayPort
• USB4 (up to 40 Gb/s)
• USB 3.1 Gen 2 (up to 10 Gb/s)

When you plug a USB-C device into a USB-C host port, the computer and the device do a little negotiation where they figure out what "blades" they have in common, and what "blades" to use.

Your Crucial X10 Pro SSD only speaks

• USB 3.2 Gen 2x2 (up to 20 Gb/s)

It does not speak Thunderbolt or USB4. It doesn't matter that the Mac can speak those at higher than 20 Gbps – the drive wouldn't understand what the Mac was saying even if the Mac did. That is a limitation of the drive. Not a "ridiculous apple thing" or even a "ridiculous USB4 thing."

Your Mac Studio supports USB 3.1 Gen 2 (up to 10Gbps), TB4 & USB4 (up to 40Gbps) and USB 3 (up to 5Gbps)

Your Crucial X10 is USB 3.2 Gen-2 2x2 (20Gb/s) ... it is not USB 4. So while it is "capable" of USB 3.x 20Gbps, your througput is limited by the USB 3.1 Gen 1 (10Gbps) of the Studio.

Also keep in mind that the speed specs are 'up to,' they are not 'guaranteed.' At 920MB/s you are getting about the max you will get with the combination of your Studio & this drive.

Aldervai wrote:

Thanks for the clarity folks. I had feared it might be something ridiculous like that. So the ports support up to 40Gb/s through TB4 / USB4, but when a drive is USB 3.2, it defaults to 3.1 with a 10Gb/s cap because Apple being Apple I guess?

I would not be at all surprised to learn that there were Windows PCs with USB4 / Thunderbolt ports that did not support USB 3.2 Gen 2x2 on those ports.

As far as USB naming, "USB 3.2" doesn't mean everything that you think it does. A full USB 3.2 name takes the form USB 3.2 Generation x Number of Lanes, where

• Generation can be 1 (5 Gbps per lane) or 2 (10 Gbps per lane)
• Number of Lanes can be 1 or 2

If one or both numbers are missing, the implication is that it is because they are 1. (You might occasionally come across a vendor who is merely using an abbreviation and not trying to imply a slow speed, but don't count on it!)

So, USB 3.2 = USB 3.2 Gen 1x1 with a maximum throughput (before overhead) of (5 Gbps/lane * 1 lane) = 5 Gbps (a.k.a. USB 3.0 speed). You need to see the full USB 3.2 Gen 2x2 for "up to 20 Gbps", and then you need to see that specification on both sides (computer and peripheral).

You can only attain the Top-Rated speeds when your external device (and all cables, of course) are sold as using those top rated protocols.

For example, ThunderBolt-5 can run at speeds above 40 G bits/sec. But it is not ONLY the port or ONLY the cables that provide the added magic. ThunderBolt-5 uses a modulated signal with multiple bits per signaling interval, and requires Port, AND Cable AND Device to talk ThunderBolt-5 for ANY speed increases. Otherwise, it falls back to slower supported protocols at slower speeds.

The "native" data rate on a USB-3 SuperSpeed cable is 10 M bits/sec FULL DUPLEX (transmitting and receiving at the exact same time) on its TWO data pathways.

To attain higher speeds, both Device and Port have to support "turning around" the interface momentarily to run both pathways inBound or both pathways outBound for a burst at 20 M bits/sec. If either does not cooperate, you are limited to 10 G bits/sec.

ThunderBolt-3 cables have four data pathways, but unless on the cable everything agrees about using ThunderBolt, they fall back to USB-3 speeds.

Macs DO NOT support the newer USB-C 3.2 Gen 2x2. There are currently none on the market. The Crucial X10 pro is the newest USB spec. Unfortunately the SSD does Not support USB4 or Thunderbolt 4 so when hooked to a Mac it will downgrade to USB-C 3.1 Gen 2 which is 10gbps. So you will max out between 800/1000 mbps read/write. Many of the drives that advertise 2000mbps R/W speeds are Gen 2x2 and unless they support USB4 or TB4 you will not get the full speeds.

Just as an aside I tested my TB5 external drive using the supplied TB5 cable with my Mac Mini M4 Pro. Then tested using a TB3 cable and no change of transfer speeds. I get >6000/5800 W/R speeds no matter what cable I used. I found this very interesting.

my notes suggest Intel ThunderBolt-3 Macs can get up to nominal 2500 M Bytes/sec on an appropriately fast SSD drive in a ThunderBolt-3 enclosure.

So your seeing the same ThunderBolt-5 calibre results over a ThunderBolt-3 cable are remarkable.

This Thunderbolt-5 is very interesting NEW technology, that Apple has just engineered from whole cloth and introduced. But it seems like there are more than a few unexpected results that were introduced with it. Some may be intentional, but others not so much.

I am also following a long thread of users complaining that using lightweight portable External displays, previously powered just fine by Thunderbolt-3 cables, mostly no longer obtaining power when connected to the Thunderbolt-5 port.

All I can say is, "It's brand new technology. Expect the ThunderBolt-5 situation to remain fluid for a while yet."

All these new drives/enclosures surprise me. I recently also got a Zikes TB4 enclosure and while it states compatible with TB3 it has poor write speeds when used on a TB3 intel Mac. I tested on my M4 Mac and no issues. On my 27" intel Mac the TB3 speeds for write were cut in half. No change on read speeds.

If you want speeds >2000 you need to use an NVME drive in a TB enclosure. You can get speeds of 2500-3000 with that setup.

There are also a few USB4 40 Gbps SSDs and SSD enclosures out now.

... and through all of that, I STILL did not get the torturous terminology right.

10 G Bits/sec is SuperSpeed PLUS, and that's what essentially every good USB-C cable can do without "tricks".