2015 iMac and Thunderbolt ports issue - Lockups!

[sbmeyer001]

Yes, my machine is getting on the old side, a 2015 iMac with 16gb of memory and quad core i7. Anyway, over the last couple of years, off and on, I find my system locked up. As a developer with some troubleshooting skills I have traced the issue to my use of the thunderbolt ports. I have two larger sized hard drives, 1TB and 2TB, that use the thunderbolt interface. I moved the 2TB to USB3, slowing the backups, but working.

I found that if I disconnect these drives from the thunderbolt ports I can reboot and things seem to work OK. In other words, when I come back to my sleeping iMac, it is NOT locked up if I stop using the thunderbolt ports. This has happened over the last 3 MacOS releases, so it is not a new problem. Today, for example, when TimeMachine was doing backups to these drives via thunderbolt, my system would just crash and reboot. Sometimes it just freezes up, no mouse, no keyboard, dead.

Again, unplug the drives from thunderbolt and the system runs fine.

Anyone have this issue, or any ideas?

Thanks

 

[ferrarr]

What brand & model are the Thunderbolt drives? Are they self powered, or Thunderbolt powered?

 

[pigoo3]

Let's be optimistic & assume there are no hardware issues...and the issue is just "macOS confusion" (from doing so much data transfer to these external drives over time).

Not sure how often these lock-ups happen...or how often you reboot the computer normally (without lockups). But maybe try rebooting the computer on a more regular basis (shorter time frame than the lockups).

Maybe doing this can clear up any "macOS confusion" before it gets to a point that the computer locks up.

Just an idea to try.

Nick

 

[sbmeyer001]

What brand & model are the Thunderbolt drives? Are they self powered, or Thunderbolt powered?

They are both Seagate. I have one that is bus powered, the 1TB, that has a built in dock (I think I can replace the drive, about the size of most portable drives.) It seems to work fine. The other is a 2TB Seagate with a dock that uses an AC adaptor. This seems to be the culprit as I have had the 1TB connected and no lockups thus far. Over the last couple of years I have had to disconnect both to prevent these freeze ups. I have played mix and match before (swapping out either drive) and had the problem. Which led me to believe it might be a bug in the thunderbolt 2 port driver. I did a backup using the USB3 ports and it was painfully slower compared to a drive connected via thunderbolt.

I am running Monterey on this 2015 21" iMac, everything else seems to work just fine. But, I have had this thunderbolt drive lockup issue over the last 3 MacOS versions, so if it is a driver issue, it is nothing they fixed.

Thanks

 

[ferrarr]

Have you tried switching cables and/or ports?

Can the 2TB drive be used without the AC adapter? Or is it a larger dimension 3x5, not small like the portable 1TB drive?

 

[sbmeyer001]

Have you tried switching cables and/or ports?

Can the 2TB drive be used without the AC adapter? Or is it a larger dimension 3x5, not small like the portable 1TB drive?

Over the last year, these drives have been connected with no issue. I did test other cables in the past which helped at that time. This freezing/lockups actually have not surfaced untill I did the latest security update for Monterey. I should have started with that fact, sorry. I was starting to think that a thunderbolt driver bug resurfaced in the update! The 2TB needs the powered dock to work. I am going to put the drive in a SATA enclosure and run some tests on it. I do not suspect the drive as this issue has been around awhile. But I will run more tests. I was just wondering if others have seen this behavior.

 

[Randy B. Singer]

...I was just wondering if others have seen this behavior.

I've certainly seen a not insubstantial number of individual USB devices that an individual Mac decides that it just hates to work properly with for some reason. Usually this happens with cheap USB hubs, but it can and has happened with any device attached via USB. (Though it just about never happens with Apple-branded USB peripherals.)

It is also not at all uncommon for an external USB hard drive to become really flaky, or fail, and to find that the internal mechanism is just fine, and when installed in a different external case, works just fine.

And, as others have indicated, it's not unusual to find that a USB cable, for whatever reason, becomes unreliable, and once you replace the cable, everything works fine.