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