as far as I know, but I am happy to stand corrected here, is that there a mix of computers on the A320. Some analogue, some digital. Some with a Intel 80186 CPU, some with a Motorola 86010.
Reason for this is that software engineers get a "spec" and design an output for a given set of input parameters. How they do it is the black box in the middle and because the hardware platforms used differ from each other, no bug can replicate itself on the other computers. Fault tolerance.
I hope that the CPU's used are radiation hardened, made using >1μm lithography and made resistant against voltage spikes and the like.
If there is an on-board OS, which I doubt, then it's probably an embedded real-time OS with ab-so-lu-te-ly not no resemblance to anything coming out of Redmond. I don't think even Bill Gates would want his IC hart monitor to run Windows...
EFB's usually run either Linux or Windows and IFE systems are the hard core CPU and RAM users.