Years ago we had a customer working on the automated control system for the Vienna main train station. They only used two computers, but one was a SPARC and the other x86. One ran using a procedural language (CHILL) from the telecom world. The other implementation was written in a production language, perhaps Prolog. they were very concerned that an identical bug could be implemented in both implementations, hence the RISC and CISC architecture and the extremely different programming paradigms.
WRONG: I believe the space shuttles started our with all the computers being LSI-11s. Presumably that was upgraded as the STS program continued!
Hmm, I looked it up and actually they were older: standard IBM avionics computers designed in the mid 1960s. They were all the same design and as far as I can tell from a little DDG searching, they were never upgraded.
I was so wrong I decided not to delete my mistaken observation.