iMac 27-inch (2020) restarts with 'x86 CPU CATERR' panic

muzammil.ahsan wrote:

<EtreCheck Report.log>

Hi Old Toad,

I have attached EtreCheck report.

I'm surprised everyone missed the second different Kernel Panic listed at the end of the report involving the Secure Enclave Processor (SEP):

2025-12-08 10:33:42 Kernel Panic (2 times)

        First occurrence: 2025-12-08 05:34:10

        Details:

            panic(cpu 0 caller 0xfffffff00f7d00b4): SEP Panic: :SEPD\/MDMA:

Since memory is tied directly to the CPU, I guess memory could be the culprit.....that or the Logic Board. Either way, if you just purchased this iMac, then I would return it and purchase a new M4 Mini instead.

If you cannot return it because it is past any return period, then you can try removing one memory stick to see if that makes any difference. If it doesn't make a difference, reinstall the memory & remove the other memory stick. This little test will tell you whether one memory stick or memory slot is bad, or whether you just have incompatible memory. Your best hope is the iMac runs fine with just a single stick of memory so you don't have to buy more since memory prices have greatly increased recently. Hard to say if mixing memory would work (one new & one old stick).

It is unfortunate the EtreCheck report doesn't list the memory slots & size of each memory stick like it has in the past.

One thing that you did not mention is the RAM configuration.

If you have added or upgraded the iMac using third-party RAM modules...?

Remove the third-party RAM modules and test iMac with only the factory modules in there original slots.

If that doesn't help, then it sounds like the iMac has a more serious hardware issue that will require Apple Service.

One thing you can do to make sure it's not software that's contributing to the problem download and run Etrecheck.  The free version is sufficient. It is strictly a diagnostic tool and the report does not involve any personal data.

Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and after clicking on the Reply button use the Additional Text button to paste the report in your reply.

Then we can examine the report and see if we can determine the cause of the problem.

+1 on posting an EtreCheck report of your system. The reason we need this is because Kernal Panics (KPs) can be caused by multiple issues from software or hardware or a combination of both. A KP report does not show what has been installed on the computer or versions of apps installed so with just the KP report all we can do is guess.

As mentioned an EtreCheck report DOES NOT post any personal or private information only what the computer's configuration is and what has been installed on it.

muzammil.ahsan wrote:

Error / Panic Log (excerpt)

panic(cpu 1 caller 0xfffffff0281cf86c): x86 CPU CATERR detected

My Questions

1. Does the error “x86 CPU CATERR detected” indicate a CPU, logic board, or power-related hardware failure?

Short answer: CATERR = CPU CATastrophic ERRor. This typically indicates a CPU hardware failure.

2. Could this be caused by SSD corruption, firmware issues, or macOS incompatibility?

Not likely.

3. Are there any Terminal commands or recovery-level steps I can try before taking the iMac to Apple Service?

You can either use the Console app, or use commands in the Terminal, to review kernel panic logs, but unless you really understand what they are telling you, you are better off to let an Apple Technician review them to provide you with your options.

muzammil.ahsan wrote:

I purchased it customized version. Originally it was with 16GB RAM, but I asked the vendor to arrange it in with 32GB RAM.

How long ago did you purchase the 2020 iMac from that vendor...?

I am not sure which RAM he installed.

iMac's are very RAM picky.

If you just purchased it from the vendor, return it for repair or a refund.

If you have had it for several years, then take it somewhere for service.

Find Locations

I would suggest that you have an Apple Technician examine your Mac. They can then advise you on your next steps. This examination should come at no cost to you. Your 2020 iMac is still considered "Supported" by Apple Support.

muzammil.ahsan wrote:

3. Are there any Terminal commands or recovery-level steps I can try before taking the iMac to Apple Service?

Make sure you have a good backup since Apple will not backup or try to recover the data on your system. Apple stopped doing this many years ago due to privacy & security concerns plus it is nearly impossible to easily backup or recover data when a Mac comes in for repair since Apple techs are not allowed to ask for a user's password.

People should have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data. FYI, there are a lot more new ways to permanently lose access to the data stored on the internal SSD of the recent Macs due to all of the hardware, software, and security changes.

A good backup should be the first priority here.

Personally I don't recommend repairing any Intel Mac (especially the USB-C models) for multiple reasons. The money spent on repairs for those systems is much better spent on a new computer IMHO. In your case instead of getting a new M-series iMac, I would recommend an M-series Mac Mini with a nice monitor.....this will be less expensive than a new iMac and you will save yourself money when you replace the Mini down the line since you will be able to continue using the external monitor so you save money once again.

In support of den.thed's recommendation of getting a new Mac Mini M4 instead of an iMac let me post the following for your consideration: a 10 Core Mac Mini M4 with 16 GB RAM and 1 TB SSD ($1084) with a 32" LG 4k monitor ($331) from Amazon.com)  is $1415 which is $541 less than a similarly configured new 24" iMac ($1956)  re 07/2025. Keep your keyboard and mouse from your current Mac for use with the Mini. 

I got the above Mini with a 32" LG 4K monitor w/speakers for only $60 more than the 27" (didn't know the Mini had a speaker).  There are many monitors available in 27" size on up for $100 to $500 depending on what features you want.  The monitor prices are before tariffs.

Just some food for thought.

den.thed has addressed most of the issues that I had except two: 1 - OpenVPN - unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these articles:  Pubic VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).    

Additionally a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

I recommend uninstalling the VPN according to the developer's instructions. Then you can check to see if you've removed all of the supporting files by downloading and running the shareware app  to search for any files with the application's or the developer's name in the file name.  For the OpenVIPN files you'd do the following search(es): 

1 - Name contains  openvpn

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac, run Find Any File again and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

2 - Apple security disabled - Apple security software is disabled. This computer is at risk of malware infection.

I don't know if the vendor who set up your Mac did it but it should be turned back on.