Spectre is a consequence of just about any speculative execution combined with shared CPU caches (or even shared memory busses, even without shared cache). Sinc

Spectre is a consequence of just about any speculative execution combined with shared CPU caches (or even shared memory busses, even without shared cache). Since nobody (including Apple) knows how to make a CPU fast without those things all high-performance CPUs are potentially vulnerable. Unless we go back to single-core single-processor systems without speculative execution (or flushing all cache on every context switch) some variant or other of a Spectre attack will be possible. If you want to be invulnerable to this you're basically stuck with a microcontroller.