I had been fighting this issue for several years, and I got to the bottom of it, so I thought I would share. (I see there are no shortage of similar reports in forums across the 'net.)
I have an "iMac (Retina 5K, 27-inch, 2017)" that is the mid-level configuration; it is a 3.5GHz quad-core i5 (4 threads) with 16GB system RAM, the Radeon Pro 575 GPU w/ 4GB option onboard, and a 256GB SSD. I have a number of external devices attached, the up-to-date list of which can be seen here:
https://bytecellar.com/the-list/#5KiMac
All worked fine as far as I could tell, and I used the system as I typically used whatever my desktop Mac at the time happened to be, with little issue. On the rare occasion I would experience a Kernel Panic, but that would happen a few times a year in general, it was my experience. But, this was in "the beforetime" (as I write this, we've just passed the 1 year mark of work-at-home for me due to the Covid-19 pandemic). This was when I spent most of my time on a computer using my work MacBook Pro, or my personal MacBook Air or iPad Pro on the couch -- the desktop Mac was typically used for photo editing here and there (which I do more and more on the iPad now) and the occasional work or personal coding (I game on PC and console). So the iMac wasn't getting a lot of use other than being the household fileserver, host of photos, music, PLEX, and backup point. Once the shutdown happened, however, I began spending all day in front of this iMac as my main development system for the day job. And that's when I started to notice the frequency of Kernel Panics...
After a month or so, I realized I was seeing a Kernel Panic every 24-36 hours, typically just after the screens awoke at the touch of a key (the system itself and its drives are set to never sleep -- just the displays). The KP report would always begin thus,
( "CATERR" is short for Intel Catastrophic Error, by the way... )
So, I dug around online and found many reports of similar incidents on iMacs and MacBook Pros, etc. Some people thought it was bad RAM. One guy took his Mac to the Genius Bar, they keyed in his S/N and were able to see the KP reports sent to Apple, and right away told him he needed a new motherboard, and they replaced it, reportedly. Others blamed external displays.
I ran the Apple Hardware Test on the system volume, but all checked out. I finally took the system to the Genius Bar and explained the entire situation. They ran some tests and all came back fine. They were willing to keep the system for a few days (ended up being a few weeks) and keep it running to see if anything happened -- it didn't. I called asking after it and was asked a few questions that set me aback. "Are you using and non-Apple peripherals with the system? Are you using any third-party software -- non-Apple software -- with the system? Which?" This line of questioning did not give me great hope of getting a resolution. I got the system back and was told to contact Apple Care via phone if it happened again and they would handle it along a different line (sending it in, apparently). Again, this seemed odd to me. I asked if the detailed reports sent to Apple at every KP showed them everything and was told that they don't have access to those.
The Genius told me to try using it without peripherals for a while and see what happened. That's somewhat difficult and so I compromised. I shifted my external data drive from Thunderbolt to USB 3.0 and my Time Machine drive from FW800 (adapted and chained off of the aforementioned disk ... precarious sounding, in retrospect) to a direct USB 2.0 attachment. Disconnected the printer (it also has WiFi printing anyway) and the Apple SuperDrive DVD drive (which I rarely use...though it is an Apple product, so, surely could not be the culprit...)
These changes made no difference at all with the crashing.
Notably here, among the attached items, is an external HP LP2065 20-inch LCD display, a 1600x1200 (4:3) unit that I am using rotated, for 1200x1600 portrait. (This would be very hard to part with, even for a few weeks, the way I work with my code and browser in web development.) I started using this display on the original Intel-based Mac Pro, later a mid-2011 iMac, and most recently this 2017 iMac (and sharing it as the display to my PowerPC-based "Amiga" when I happen to use it). I like the display and, while it was manufactured over 15 years ago, I recently replaced it when my original failed with a New-In-Box display of the same model. It's a nice screen, even if it's lit with fluorescent tech rather than LED. Given its age, however, DVI is its connection interface (it has two). Given this, I required a USB-C to DVI adapter/cable to get the unit working on this iMac when I made the purchase.
To connect the screen to the iMac I purchased one of many cables on offer that I found at Amazon. Looking at my purchase history, the unit was entitled (at some length),
And it looked like this:
A single cable with whatever electronics needed for conversion obviously in the DVI connector assembly.
Thinking this might be the problem (as mentioned, some spoke of external displays as what they felt was the issue, in the forums), I ordered another such adapter at random, just from a different vendor. It arrived ... and looked, physically, exactly the same as the one I was replacing. It was listed at Amazon as:
I put it in place ... and the KPs continued.
After enduring this incessant crashing for a few weeks more I tried a clearly different (and intentionally more expensive - but not very) adapter type, one that went from USB-C to a female DVI connector on a short cable -- at least it was definitely no the same cable I'd been using. The unit I purchased (from NewEgg this time) was the
And it looks like this:
I removed the old cable, put this in place with a standard male-to-male DVI cable, and crossed my fingers.
And, I am happy to report, that the uptime of this system is just under 112 days -- just under 4 months! The USB-C-to-DVI adapter(s) I had been using were the culprit, and my crashes are no more.
I am posting this in hopes that someone else facing such issues may benefit from my experience, if the cause of their issue happens to be the same as mine.
bp
t: @blakespot
I have an "iMac (Retina 5K, 27-inch, 2017)" that is the mid-level configuration; it is a 3.5GHz quad-core i5 (4 threads) with 16GB system RAM, the Radeon Pro 575 GPU w/ 4GB option onboard, and a 256GB SSD. I have a number of external devices attached, the up-to-date list of which can be seen here:
https://bytecellar.com/the-list/#5KiMac
All worked fine as far as I could tell, and I used the system as I typically used whatever my desktop Mac at the time happened to be, with little issue. On the rare occasion I would experience a Kernel Panic, but that would happen a few times a year in general, it was my experience. But, this was in "the beforetime" (as I write this, we've just passed the 1 year mark of work-at-home for me due to the Covid-19 pandemic). This was when I spent most of my time on a computer using my work MacBook Pro, or my personal MacBook Air or iPad Pro on the couch -- the desktop Mac was typically used for photo editing here and there (which I do more and more on the iPad now) and the occasional work or personal coding (I game on PC and console). So the iMac wasn't getting a lot of use other than being the household fileserver, host of photos, music, PLEX, and backup point. Once the shutdown happened, however, I began spending all day in front of this iMac as my main development system for the day job. And that's when I started to notice the frequency of Kernel Panics...
After a month or so, I realized I was seeing a Kernel Panic every 24-36 hours, typically just after the screens awoke at the touch of a key (the system itself and its drives are set to never sleep -- just the displays). The KP report would always begin thus,
( "CATERR" is short for Intel Catastrophic Error, by the way... )
So, I dug around online and found many reports of similar incidents on iMacs and MacBook Pros, etc. Some people thought it was bad RAM. One guy took his Mac to the Genius Bar, they keyed in his S/N and were able to see the KP reports sent to Apple, and right away told him he needed a new motherboard, and they replaced it, reportedly. Others blamed external displays.
I ran the Apple Hardware Test on the system volume, but all checked out. I finally took the system to the Genius Bar and explained the entire situation. They ran some tests and all came back fine. They were willing to keep the system for a few days (ended up being a few weeks) and keep it running to see if anything happened -- it didn't. I called asking after it and was asked a few questions that set me aback. "Are you using and non-Apple peripherals with the system? Are you using any third-party software -- non-Apple software -- with the system? Which?" This line of questioning did not give me great hope of getting a resolution. I got the system back and was told to contact Apple Care via phone if it happened again and they would handle it along a different line (sending it in, apparently). Again, this seemed odd to me. I asked if the detailed reports sent to Apple at every KP showed them everything and was told that they don't have access to those.
The Genius told me to try using it without peripherals for a while and see what happened. That's somewhat difficult and so I compromised. I shifted my external data drive from Thunderbolt to USB 3.0 and my Time Machine drive from FW800 (adapted and chained off of the aforementioned disk ... precarious sounding, in retrospect) to a direct USB 2.0 attachment. Disconnected the printer (it also has WiFi printing anyway) and the Apple SuperDrive DVD drive (which I rarely use...though it is an Apple product, so, surely could not be the culprit...)
These changes made no difference at all with the crashing.
Notably here, among the attached items, is an external HP LP2065 20-inch LCD display, a 1600x1200 (4:3) unit that I am using rotated, for 1200x1600 portrait. (This would be very hard to part with, even for a few weeks, the way I work with my code and browser in web development.) I started using this display on the original Intel-based Mac Pro, later a mid-2011 iMac, and most recently this 2017 iMac (and sharing it as the display to my PowerPC-based "Amiga" when I happen to use it). I like the display and, while it was manufactured over 15 years ago, I recently replaced it when my original failed with a New-In-Box display of the same model. It's a nice screen, even if it's lit with fluorescent tech rather than LED. Given its age, however, DVI is its connection interface (it has two). Given this, I required a USB-C to DVI adapter/cable to get the unit working on this iMac when I made the purchase.
To connect the screen to the iMac I purchased one of many cables on offer that I found at Amazon. Looking at my purchase history, the unit was entitled (at some length),
And it looked like this:
A single cable with whatever electronics needed for conversion obviously in the DVI connector assembly.
Thinking this might be the problem (as mentioned, some spoke of external displays as what they felt was the issue, in the forums), I ordered another such adapter at random, just from a different vendor. It arrived ... and looked, physically, exactly the same as the one I was replacing. It was listed at Amazon as:
I put it in place ... and the KPs continued.
After enduring this incessant crashing for a few weeks more I tried a clearly different (and intentionally more expensive - but not very) adapter type, one that went from USB-C to a female DVI connector on a short cable -- at least it was definitely no the same cable I'd been using. The unit I purchased (from NewEgg this time) was the
And it looks like this:
I removed the old cable, put this in place with a standard male-to-male DVI cable, and crossed my fingers.
And, I am happy to report, that the uptime of this system is just under 112 days -- just under 4 months! The USB-C-to-DVI adapter(s) I had been using were the culprit, and my crashes are no more.
I am posting this in hopes that someone else facing such issues may benefit from my experience, if the cause of their issue happens to be the same as mine.
bp
t: @blakespot
