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

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:

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.