USB SSD Drive Speed "Limited to 5 Gb/s"

DMBP24 wrote:

I have the same issue with the OWC Elite Pro Dual Mini on the Mac Studio 2023 M2 Ultra. When the iPhone 15 Pro with the USB-C port is connected to the Mac Studio it only functions at 480 Mb/s.

The 480MB/s indicates a USB2 transfer rate. It would not surprise me that the Apple supplied charging cable would be limited to USB2 speeds since that is what Apple did with the USB-C charging cables for their laptops.

Here is an Apple article with the details, but I will copy the relevant section here:

Charge and connect with the USB-C connector on your iPhone 15 - Apple Support

Your iPhone will charge while connected to these devices. iPhone 15 Pro and iPhone 15 Pro Max support fast USB 3.2 Gen 2 speeds up to 10Gbit per second when using an optional USB 3 cable.1

And here is the footnote denoted by the trailing "1" in the above quote where I'm highlighting sections in bold:

1. The USB-C cable that comes with your iPhone supports charging and USB 2 speeds. If you want to use a USB 3 device, use a compliant USB 3 cable that supports 10Gbit/s.

You need to purchase a USB3 USB-C cable to get faster speeds.

Yes, the whole USB-C port/connection is completely messed up & extremely hard to comprehend. USB-C is just the type of connector. USB-C does not denote any type of specific transfer protocols on its own. In fact, you can have a USB-C charging only cable which is unable to transfer any data. You must pay careful attention to any listed specifications for any devices which utilize USB-C connectors (this includes cables as well).

Here is an Apple USB-C cable capable of supporting USB3 speeds & protocols which Apple calls a Thunderbolt 3 cable since it also supports the Thunderbolt 3 protocols:

About the Apple Thunderbolt 3 (USB-C) Cable - Apple Support

That's the design criteria. "Why" type questions are the domain of Apple programmers and the R&D department and Apple famously is tight lipped.

For our Macs, USB-A ports are limited to about 480 GB/s; USB-C ports will approach the SSD limit of 1050 GB/s with consistent speeds in the 1030 GB/s range.

You're on the USB 3.1 bus

Breaking down USB data transfer rates

• USB 5 Gbps: The specification name is USB 3.2 Gen 1, which used to be called USB 3.0. It offers a transfer rate of 5 Gbps, which is about 10 times faster than the USB 2.0 standard.
• USB 10 Gbps: The specification name is USB 3.2 Gen 2 (released in July 2013) and it used to be called USB 3.1. It offers a transfer rate of 10 Gbps over the existing USB-A and USB-C connectors.
• USB 20 Gbps: The specification name is USB 3.2 Gen 2×2 (released in September 2017) and it is available only for USB Type-C connectors using two-lane operation. It offers 20 Gbps transfer speeds.
• USB 40 Gbps: The specification name is USB4 (released in March 2019). It leverages the Thunderbolt 3 protocol and offers transfer speeds of 40 Gbps. (Note that the correct specification name is USB4 as defined by the USB developers. It is sometimes identified as USB 4 with a space.) 
• USB 80 Gbps: The specification name is USB4 Version 2.0 (released in October 2022). This updated specification extends USB4 speed and data protocol performance, enabling manufacturers to develop products that can deliver up to 80 Gbps transfer speeds.
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But these are all theoretical max laboratory speeds. Your exact setup is likely not lab grade.

Because of the nebulous USB specs these days, manufacturers can be quite loosy goosey in their claims.

What is not clearly spelled out on the Mac is that it supports USB 3.1 Gen 2 single lane. Even though it can support 10Gb/s, the device must support that speed over a single lane.

On the other hand, SanDisk's claim of 10Gb/s speed with USB 3.2 Gen 2 is only achieved if the host device supports dual lane USB transfers, which they totally fail to mention.

So, the SanDisk device can only deliver half the claimed speed since there is only one lane available.

The whole USB specification has become a totally nebulous ball of wax and now with USB4 it is only getting worse. You need a scorecard to keep track of what each generation is capable and all the variations that can be implemented but not required.

The real world speed of any external drive is determined by the port and cable used.

Specs for the drive are the best you can ever expect under perfect laboratory conditions. They are essentially a marketing approach, are theoretical and seldom actually achieved.

Oh +1

I have the same issue with the OWC Elite Pro Dual Mini on the Mac Studio 2023 M2 Ultra. When the iPhone 15 Pro with the USB-C port is connected to the Mac Studio it only functions at 480 Mb/s.