fed-l1c-iside-parity — Processor / logic board

The hardware error handler of the “Firestorm” performance cores (A14 / M1 chips) detected a parity error in the level 1 instruction cache (L1C, I side): data read from the cache no longer matched its check bit. This is an error detected by the processor hardware, not an app bug. The exact same string (@AppleFireStormErrorHandler.cpp:599) appears on an M1 MacBook Air, with different apps at the time of the crash; REWA classifies “fed err (parity…)” under NAND / SoC. An isolated case may be a transient error; repeats point to the SoC or its power supply on the logic board.