USB 3 devices runs at USB 2 speed on MacBook Pro's USB-C

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Level 1

9 points

USB 3 devices runs at USB 2 speed on MacBook Pro's USB-C

Hi,

I have been struggling since day one with my USB-C connections. It has always been rather slow for backup's by example. Once it even stopped charging. With different SMC resets I could recover from this one but never get to a full speed USB3. When I go to system report and click on the USB items it does show my USB3.0 devices but with speed of up to 480MB/s.

When I connect different USB HD and SSDs and use Black Magic it never goes beyond 40Mb/s in read and write while on my former MacBook Pro (13" Retina 2014) those devices go well beyond 120 Mb/s. Besides some of my USB 3 HD have a LED that shows USB 2 vs. USB 3 speed. On my MacBook Pro 2018 USBC connection it always shows USB2 speed and this independently of the adapters/cable I use.

I have been using different USB-C to USB 2 female adapters with USB3 or USBC cables that otherwise deliver full speed on my older MacBook Pro.

Lately I also tried a NVRAM reset with no success.

Long story short: I start to doubt in the health of my MacBook Pro. Is this a know problem? Any suggestion?

Thanks.

MacBook Pro TouchBar and Touch ID, macOS High Sierra (10.13.5), 13"

Posted on Jul 8, 2018 4:56 AM

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Answer 1

Best reply

Grant Bennet-Alder

Level 10

127,195 points

Jul 9, 2018 10:29 AM in response to jpservices

another way of explaining this:

ThunderBolt-3 is an uncommitted computer port that can do almost anything, with the right cables/adapters. The first cable/adapter you attach specializes the port to one particular purpose, usually a more narrow subset of all it could potentially do.

To use genuine ThunderBolt devices, you must do that customization with a ThunderBolt cable/adapter. Others will not have all the wiring needed to support ThunderBolt. (example: the Mac charging cable plugs into that port, but supports ONLY charging or USB-2, and nothing more.)

DO NOT assume all cables are equal when it comes to connecting to these ports. Those days Are GONE FOREVER.

Each and every cable must be examined in detail for its capabilities. Cables that look identical WILL behave differently.

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Answer 2

Jul 8, 2018 10:00 AM in response to jpservices

About Thunderbolt 3

MacBook Pro (15-inch, 2016), MacBook Pro (13-inch, 2016, Four Thunderbolt 3 Ports), and MacBook Pro (13-inch, 2016, Two Thunderbolt 3 Ports) come equipped with Thunderbolt 3, an I/O technology that connects devices to your computer at speeds up to 40 Gbps. Thunderbolt 3 combines data transfer, video output, and charging capabilities in a single, compact connector.

The Thunderbolt 3 (USB-C) ports on your MacBook Pro support Thunderbolt 3 devices at speeds up to 40 Gbps when you use a Thunderbolt 3 (USB-C to USB-C) cable. You can also connect Thunderbolt and Thunderbolt 2 devices using the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter at maximum speeds of 20 Gbps. Learn more about Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter compatibility.

from:

Connect with Thunderbolt 3 on your new MacBook Pro - Apple Support

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Answer 3

jpservices Author

Level 1

9 points

Jul 9, 2018 10:36 AM in response to Grant Bennet-Alder

Thanks to Grant Bennet-Adler. This make sense. Now: if I have an adapter that is claiming that it converts "USB 3.1 Type-C Male To USB 3.0 Female" can I assume that if I connect this adapter together with a USB 3 drives and cable that it should run at USB 3 speed? Or is this more complexe?

Thanks

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Answer 4

Jul 9, 2018 8:46 PM in response to jpservices

That sounds great, and is not more complex.

You never used to have tho think about it at all -- if it fit, it would work. Not now.

The big mistakes Users are making is things like assuming the charge cable will do USB-3. It fits -- but does not work.

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Answer 5

jpservices Author

Level 1

9 points

Jul 11, 2018 11:55 AM in response to Grant Bennet-Alder

Thanks for the help. Even with my USB-C to USB 3.1 adapters and a USB 3.0 cable that was proven to work at full speed on my older MacBook Pro I cannot reach more than the 480MB/s. Next step is to try on an other MacBook Pro that has USB C to start to frame the problem. I start to seriously doubt in the health of my MacBook Pro....

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