Originally Posted by
peekay4
Probably not even that... the 486 didn't exist when the A320 entered service. Most A320s run 286s; some very early ones had 186s.
Someone made the decision that computers for safety critical systems had to be 'formally proved' by mathematics. This was difficult but just about achievable with 'simple' 286 chips with a single core and nothing really clever in its operation. However, with multicore CPUs which are effectively a set of computers working together all dropping and picking up threads of programs, pre-fetching expected code branches based on algorithms, being pre-empted and picking up a new thread etc etc., formal proof becomes impossible or at least an nP problem. Certification testing is going to have to change as it makes no sense to restrict the capability of the CPU in the FMC in this way.