Laptop that throttles under load

Thermal throttling. Check the sustained clock with a monitor running, then decide between undervolting, a lower power limit that trades peak for consistency, or a cooling pad. The consistent lower clock usually finishes builds faster than the sawtooth.

For a filesystem that checksums data, ECC protects the one place checksums cannot: memory between verification and write. It is not mandatory, and the honest framing is insurance whose premium is a slightly more expensive board.