(your favourite!) x86 was utilized extensively with Windoze garbage and that marriage abomination manifested into ATMs and POSs, airport terminals etc. Security nightmare.
yup, from 1997 to today I have collected something like ~300 photos of airport, railway, underground (even in the UK), or ship information terminals, showing a genuine Windows crash.
I've seen tactical engines filled with bullet holes in their structures causing the CBIT (continuous bit testing, kind of low level perpetual diagnistic) to report the catastropic diagnostic "main system failure, 10% operation", then hardware 90% destroyed, yet the Voter disconneted the damaged board, and the emergency software running on the reduncancy subsystem still able to bring back both the black box and the rest.
on x86 ... it's a serious problem to run this
mov eax,cr0 ; get CPU control register
; 286 will resume execution @ 0xF000:FFF0
; 386 will fall through.
lidt [reset_IDTR]
; restore real-mode compatible value
; * * * mandatory * * *
; real-mode interrupts are relocatable
; on the 386 via the IDT register!
and eax,0xfffffffe ; clear protected mode bit
mov cr0,eax ; now, the cpu is out of protected-mode
;----------------------------------------------------------------------------
as it causes a triple-fault, and it may fail, resulting a system that no more powerup. Yup, you can add a WDT ... but it's not a smart idea for the Voter because if the CPUs don't respond to the CBIT you might trick the Voter into thinking that the CPUs are damaged.
so, it's why x86 is no good for for MTC stuff, while PowerPC is the preferred choice.
Of both m88k and i960 I have seen mission tactical computer MTCs (military stuff) for tactical with two CPUs connected to an "intrinsically safe" Voter-circuit. I saw despite both the hardware and software complexity is high, it looked simpler than other modern approaches, even simpler and more fault-tollerant than tri-cores all-in-one solutions.
Really impressed