Apple Event: May 7th at 7 am PT
As part of my job, I often have to make disk duplicates using Balena Etcher software.
I did have a 2019 iMac (intel) that could run 4 images in about 5 mins.
I now have a brand new Mac Studio M2, and it takes 90 minutes!
I am using the USB-C connections on the front and rear (Different Bus).
But why is it SO MUCH SLOWER than before?
Mac Studio (2023)
On a Mac Studio MAX (not Ultra), the USB-C ports on the front are limited to 10 G bits/sec.
The Thunderbolt ports on the rear max out at 40 G bits/sec with genuine thunderbolt cables and thunderbolt devices, 20 G with USB-C
But a typical USB reader is far slower than a USB Bus.
Mac Studio - Technical Specifications - Apple
On a Mac Studio MAX (not Ultra), the USB-C ports on the front are limited to 10 G bits/sec.
The Thunderbolt ports on the rear max out at 40 G bits/sec with genuine thunderbolt cables and thunderbolt devices, 20 G with USB-C
But a typical USB reader is far slower than a USB Bus.
Mac Studio - Technical Specifications - Apple
Grant Bennet-Alder wrote:
I would welcome any authoritative source (or user experiences) that clarifies these ports actual maximum speed as USB-C ports.
I'm going by reports that I have seen that when people connected USB 3.2 Gen 2x2 SSDs to Macs with USB-C (Thunderbolt) ports, connections did not occur at USB 3.2 Gen 2x2, but fell back to USB 3.1 Gen 2 speed. This was probably with respect to Macs other than Studios – but, nonetheless, Macs that were capable of running at "up to 40 Gbps" when using Thunderbolt protocol.
A quick Google search turns up things like:
USB 3.2 Gen 2x2 on Thunderbolt 4 - Apple Community – where someone reported that the M1 MacBook Pro was incapable of delivering USB 3.2 Gen 2x2 speed.
https://macperformanceguide.com/blog/2023/20230328_1407-DoMacsSupportUSB_C-Gen3_2.2.html – where the answer to the question ("Do Macs support USB 3.2 Gen 2x2?") appeared to be No, but wasn't entirely clear.
https://www.quora.com/Why-does-the-MacBook-Pro-only-support-Thunderbolt-3-40-Gbps-and-USB-C-3-2-gen-2-10-Gbps-but-not-USB-C-3-2-gen-2-2-20-Gbps, which claims that the USB 3.2 Gen 2x2 specifications were not ready in time to be included in Thunderbolt 3, and that USB4 merged the specifications. I don't know whether I buy this, but then, there are some aspects of USB4 that seem unnecessarily confusing.
Grant Bennet-Alder wrote:
https://discussions.apple.com/content/attachment/d6c7aed6-8a8d-4332-af08-f160ffa18868
This chart is not my work, likely from Wikipedia
USB mode naming is another minefield.
The USB 3.1 standard includes
A vendor might advertise a port as a "USB 3.1" port even though it only runs at "up to 5 Gbps".
Likewise with USB 3.2, if you want the "up to 20 Gbps" speed, you need to check for the full "Gen 2x2" part. There are USB 3.2 names corresponding to USB 3.0 and USB 3.1 Gen 2 speeds.
At least with USB 3.x, if you match the (implicit) generation and (implicit) number of lanes, you're (probably) talking about the same mode. With USB4,
Happy, happy, joy, joy!
Some Reader comments I found claim that the USB-C in the front USB-C ports of the ordinary Mac Studio Max (not Ultra) are two Busses driven by one ASM3142 Controller chip (or equivalent circuitry) powered by x1 PCIe lane at around 8 G Transfers/sec, equivalent to 8 G bits/sec.. That would explain the slower speeds on the front USB-C ports.
It was also interesting to note that nominal connection speed could readily be seen in:
Menu > About this Mac > (system report) > ThunderBolt (or USB)
This chart is not my work, likely from Wikipedia
Grant Bennet-Alder wrote:
On a Mac Studio MAX (not Ultra), the USB-C ports on the front are limited to 10 G bits/sec.
The Thunderbolt ports on the rear max out at 40 G bits/sec with genuine thunderbolt cables and thunderbolt devices, 20 G with USB-C
I could be wrong, but I believe that the rear-panel USB4 ports do not support USB 3.2 Gen 2x2. So until there are USB4 20 Gbps and USB4 40 Gbps peripherals, the practical limit on USB transfer speeds will be "up to 10 Gbps" (USB 3.1 Gen 2 speed).
A "full featured" USB-C cable is specified as USB 3.1, SuperSpeed+, capable of 10 G bits/sec. The way any USB-C port attains USB-C 3.2 2x2, 20 G bits/sec speed is to momentarily 'turn around' the inbound data pathways and use them as all outbound, (or the reverse) then return to normal.
For the front USB-C only ports, they are generated outside the system-on-a-chip using hardware that does not 'turn around', and does not support speeds higher than 10 G bits/sec. That implementation was made simpler by not supporting turning around and not supporting a higher data rate.
The ThunderBolt ports are full featured 40 G bits/sec ports, whose ferocious data rates are created deep inside the system-on-a-chip. To get that specified total data rate, the outbound data pathways must 'turn around' (or the reverse).
Aside: that's why the Ultra, two system-on-a-chip welded together with double-speed access to RAM, can easily create TWO sets of ThunderBolt ports.
So I do not see a compelling reason why the ThunderBolt ports, when used for USB-C data, would need to be limited to only 10 G bits/sec. They already have the electrical ability to be turned around, and they have the higher data rates available.
So I ASSUMED the data rates for USB-C on those ports DID support 20 G bits/sec. I confess, I do not have a document at hand that confirms or denies my assumption.
I would welcome any authoritative source (or user experiences) that clarifies these ports actual maximum speed as USB-C ports.
I'm obviously not a frequent poster but I just noticed something interesting while playing around with my 2019 MacBook Pro 15 in with intel i7 processor. Perhaps this is clear from the other posts. If so, sorry for wasting your time. Several years ago I purchased an external ssd that was supposed to deliver usb-c 3.2 Gen 2x2 speed. With my Mac it didn't. Today I was using several of the ports so I plugged in a hub I had sitting around. I forget the brand although I could probably figure it out. Anyway, I assumed that it would be very slow and was curious how slow, so I ran a speed test with blackmagic. Surprise: the write speed was around 1050MB/s and the read speed was 2612 MB/s. I didn't think that was even possible with all the right equipment.
Might also be a good idea to ask in the Balena Forum.
Thunderbolt (USB-C) speeds
