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  • Writer's pictureGeorge Napier

Into the Seven Circles...

It worked just great yesterday...

I've spent the better part of the last three or four days being in that place NONE of us want to be with our set up. Namely, trying to figure out why something that worked reasonably well devolved into an unstable, unusable mess.

The gremlin that struck me is a well known one apparently as there are lots of posts and discussions about it easily found with a quick Google Search. Basically a Mac running Catalina and left idle will sometimes develop a kernel panic and spontaneously re-boot.

This behavior can occur very rarely (every few days/weeks) or quite often (every 10 minutes). It can be related to loaded extensions ('kext') or attached hardware. It seems like it can happen for as many reasons as there are unique system configurations - although most of the issues seem to point to some underlying problem in the OS.

How do you know if this has happened to you? Well, besides the machine suddenly re-booting, it will produce a crash report to send to Apple. That report will contain a line like this:

panic(cpu 6 caller 0xffffff7f8879cad5): userspace watchdog timeout: no successful checkins from in 140 seconds

I wanted to find out what was going on (as this was new behavior) and of course how to stop it. After a lot of searching, I found useful leads at Apple's community forums ( And there - over the last several days - I shared my observations and experiences. As I was reviewing it, it read a bit like a journal...or a prisoner's diary.

Dec 24, 2020 2:21 PM in response to ****slav276

The problems didn't start UNTIL I installed the latest Catalina Security update for 10.15.7. It was sporadic at first, then it occurred daily, now it's happened 6 times in the last hour. I've been all over the internet reading support threads at Apple and discussions elsewhere.... Since this is also happening on the M1 Macs and Big Sur, Apple must surely understand this is a real issue, no?

My set up is quite complex as I'm running an extensive recording set-up with all kinds of hardware and multiple visual monitors connected to an iMacPro 10 core 64gb/4TB machine. Because of that complexity, I do not expect Apple Support to be any help whatsoever; There are too many other things they can point to as the possible culprit. I don't know...could be legit, but the thing is this: It was stable and operating near perfectly before this latest update. Now, I'm afraid to walk away from it for more than 10 minutes....

Dec 25, 2020 4:14 AM in response to****slav276

Some hopeful news on my front!

My crashes were coming like clockwork every 760 seconds or so. (I want to restate: It was nothing like this before the last Catalina security update I installed a few days ago.)

I started disconnecting attached hardware to see if the behavior changed. Disconnecting my Drobo 5c made no difference. Disconnecting my external drive enclosure (OWC TB3 ThunderBay 8) made no difference. Disconnecting 2 of my 5 monitors by removing an OWC Thunderbolt 3 Mini Dock w/HDMI 2.0 made no difference. (I have worked with three monitors with this iMac from day one with no problems, but I recently added 2 more monitors in other parts of my studio for ergonomics.) The crashes kept coming.

However, I have a UAD card in an external closure (Sonnet Echo Express SE1 Thunderbolt 3 Expansion Chassis). I removed that, and there have been NO crashes overnight!! Running the UAD card in the enclosure has mostly been a set and forget affair, but there is the occasional unexplained system “hiccup.” (But again, nothing like constant crashing before the Apple Catalina security update the other day.)

My game plan now is to begin reattaching things one at a time to test for stability. I am going to start with an update of the UAD software to the latest version and reattach the enclosure to see what happens. I really don’t want to have to walk away from my UAD plugins considering their utility and investment!

Even if I get that to work, I’ll detach it and connect another piece solo to test. Once I’m sure which ones work ok in isolation, I’ll reattach them all at the same time.

(Well, at least I know what I’ll be doing most of Christmas Day!)

I don’t know if you have an analogous piece of equipment but, if you do, give it a hard look!

Best regards.

Dec 26, 2020 5:26 AM in response to *****er


I downloaded the new UAD software and reattached the Sonnet echo express. No crash for over an hour. I then reconnected the OWC mini dock and two monitors. No crash for over an hour. I then reconnected the OWC Thunderbay 8...and all **** broke loose.

Near as I could figure at the time, it’s was coming down to one of two things: A particular drive in the Thunderbay appears to be problematic and may be causing an issue, OR the fact that the Sonnet and Thunderbay are daisy chained may be causing an issue. I decided that I would explore both options tomorrow, so I unplugged the Thunderbay leaving only the Sonnet box attached. I thought everything solid.

However, after 7.58 hours, the panic and crash happened. I shutdown the machine, restarted logged in...and a few minutes later it happened again.

The only thing connected or powered up is the Sonnet box. Why would that configuration have been stable for 8 hours then suddenly start being flaky? It makes NO SENSE.

I disconnected the sonnet box and rebooted and logged in to see if the iMac Pro could make it through the night by itself. It didn’t. So this isn’t about just connections to external gear. Apparently I could fix all of that, and it wouldn’t matter because with no external gear attached/powered on it will still re-boot.

I’ve owned Apple products since the early 90s. I sold Apple computers 20 years ago. Buddies accuse me of being a fanboy. But this is fast becoming my worst Apple experience to date.

Dec 27, 2020 5:30 AM in response to ****r

Ok. Another update.

I replaced the problematic drive in the Thunderbay 8. I attached it back to the iMac. I also reattached my Drobo 5c so I could clone the content of the old drive on to the new one.

All of that proceeded without a hitch. So I decided to leave the set-up running to find out how long it would operate without a kernel panic. So far this set up has remained up and operational with no reboots for over 12 hours.

To recap: Directly attached to the computer and operational is the Thunderbay 8 via TB3, a CalDigit TS3 Plus 15-Port TB3 Dock, a MOTU 1248 via TB2/TB3, and an OWC TB3 dual HDMI mini Dock. There’s also a USB 3 hub and various USB devices (mostly synthesizers and modules) connected to the iMac. Essentially, the only thing NOT attached is the Sonnet Echo Express SE I...

I’ll leave the Sonnet box disconnected and see how long this lasts, but if it stays stable then my investment in UAD gear may be toast...

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