A 486dx4 is about four to six times faster than the microprocessor used in the space shuttle, the AP-101S :) Older processors can be manufactured to withstand a combat environment, plus they have been used for so many years that any bugs might have been ironed out, haha.
I wonder what processor the longbow has, but I guess that it will be crushed by your PC :) But hey, they don't need to run windows on top of it!