Many CPUs have been used in space craft, space stations
and other such probes.
Such CPUs must be highly reliable, and very durable. The temperatures
in space, even
with heaters, can vary widely. The radiation that a system is exposed
too can be immense.
So when designing one of these systems designers don't always use the
latest and greatest
microprocessor. They use a chip that has been tried and tested. That
they KNOW will work.
A CPU for use in space must first be MIL-STD-883 (usually Class M or S, ground based is B). This
means it has met the over 100 tests