USB 3 Drive Only Negotiating a 480Mbps Speed in Big Sur

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Level 3

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USB 3 Drive Only Negotiating a 480Mbps Speed in Big Sur

I have a variety of external drives, most of which are USB 3. They all connect via a USB-C to Micro B 3.0 cable. I connect it to an open plug on the 2020 MBA (Intel) and it has always negotiated the fastest speed available. Now, it's only working at USB 2 speed. See screenshot for an example. It recognizes the enclosure correctly as an External USB 3.0, but won't go the full speed.

Running 11.4, latest non-beta version of Big Sur.

MacBook Air 13″, macOS 11.4

Posted on Jul 17, 2021 12:54 PM

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Answer 1

Best reply

Old Toad

Level 10

207,787 points

Jul 17, 2021 2:23 PM in response to umparrothead

A long shot but boot into Safe Mode according to Start up your Mac in safe mode - Apple Support and test the disk speed to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to nearly twice as long as a normal boot as it's doing the following;

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts

• Deletes font caches, kernel cache, and other system cache files

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Answer 2

Jul 17, 2021 2:35 PM in response to umparrothead

Nice informative post.

“Cable” was the first thought that popped into my mind too … even before reading the replies.

Apple sells a Mophie version in it’s store. I’d probably start w/ in an effort to eliminate as many unknown variables as possible.

https://store.apple.com/xc/product/HN8D2ZM/A

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Answer 3

umparrothead Author

Level 3

756 points

Jul 17, 2021 1:59 PM in response to Barney-15E

That was my first thought, too. I didn't have any others available, but will soon, and plan to test that. Nothing else on the same bus, except power if it's there (official Apple cable), but not at the same time.

All my drives are behaving this way.

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Answer 4

umparrothead Author

Level 3

756 points

Jul 17, 2021 8:34 PM in response to Barney-15E

Great point, forgot about SMC. Did the Safe Boot as a first step.

Tried another cable, rather, a USB C hub with a USB A-Micro B cable, and all the drives negotiated a 5Gbps speed (and based on performance, definitely seem to be achieving it).

Then, used the other cable again, and it's providing the 5Gbps speed too.

Currently copying files to separate drives, both at a high speed. I'll see about getting that cable replaced if it's intermittent. Thanks all for the suggestions!

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Answer 5

Barney-15E

Level 10

112,926 points

Jul 17, 2021 1:49 PM in response to umparrothead

Try a different cable.

It doesn't appear anything else is on the same bus.

Any other drives doing this?

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Answer 6

Barney-15E

Level 10

112,926 points

Jul 17, 2021 4:52 PM in response to umparrothead

Not sure it controls the USB ports, but maybe try an SMC reset since it is an Intel Mac.

How to reset the SMC of your Mac - Apple Support

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Answer 7

umparrothead Author

Level 3

756 points

Jul 17, 2021 3:13 PM in response to Chattanoogan

Thanks all. Yes, cable is hopefully the issue and I'm getting another to test later tonight. In the meantime, a Safe Mode boot probably couldn't hurt cleaning the OS out a bit.

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USB 3 Drive Only Negotiating a 480Mbps Speed in Big Sur

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