MacBook 2021 restart panic cpu 6

<< panic(cpu 6 [...] "FED err (L1C I-side data parity) on P-core: >>

...that says CPU 6 pre-fetched a word INTO its level 1 cache and that word was WRONG. It has a parity error on input.

if you have more than one of these messages, you have a serious Hardware error. No amount of goofy software can make this very low level Hardware error happen.

Some panic-reasons suggest a Hardware issue. There is a procedure that can allow you to find more of those reports to look for more of the same panic reason. Ask for assistance if you need it.

The telephone support people are more likely to work with you to eliminate obvious common issues. They are NOT trained to read panic reports. They will insist that you go through the motions to eliminate software issues. But when they get to the end of their list, you should insist on having your problem escalated to a specialist. Specialists are more likely to actually read your panic reports, and to agree this is a problem and DIRECT an Apple service provider to swap things (likely mainboard) for a new one.

if you take it to an Apple service provider first, they will likely run diagnostics, report no fault found, and return it to you unchanged. They are generally not trained to read panic reports.

You MUST have a Trusted backup before submitting your Mac for service. if the mainboard is swapped out, the boot drive will be swapped out as well, and you will not get your files back.

CPU 6 is not the key -- the words after it, especially the word PARITY are the important part.