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iMac M1 (2021) Thunderbolt port inconsistency

Hi!

I have a 2 USB + 2 TB3/USB4 model.

The issue is external self powered TB drives not mounting after a Restart or Power on.

If my drives are plugged into the outside TB port (one to the right in the photo), they mount normally and there is no issue.

If they are plugged into the inside TB port, they will not mount. The drives need to be power cycled to mount. It doesn’t matter if it’s from a system restart/reboot or powering up for the first time. Without the power cycle, no drives.

Discovered this behavior troubleshooting other issues with this iMac….and there are many as far as a video editor is concerned. (use a Logitech MX Master 2S at your own peril with Premiere and Media Encoder)

What is the difference in the ports? Is this a sign of a defective port? I’m not finding anything that documents any differences in the ports. Since each one is its own bus, I can’t help but feel I have a defective port.

iMac Line (2012 and Later)

Posted on Sep 3, 2021 11:04 AM

Best reply

Old Toad

Level 10

207,883 points

Posted on Sep 3, 2021 1:02 PM

You should still be within the 1 year warranty period so contact AppleCare and get a diagnostic of your M1 to determine if it is hardware related or not. Be sure to make a full backup of the drive before taking it in as they may erase the drive and reinstall a pristine system to verify that it's not software related.

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iMac M1 (2021) Thunderbolt port inconsistency

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