The ARM processor has come a long way from an obscure British microprocessor of the 1980's to being the dominant basis for the current generation of smart phones, and tablet computers, as well as its use in space They are also in television set-top boxes, routers, and embedded applications. The ARM architecture units represent the highest volume of 32-bit processors being shipped, as of this writing.
ARM's can be found on space missions, most likely in Cubesats, but also on the ISS. At the moment there are several models of a rad-hard Arduino-class microcontroller, and an ongoing NASA-USAF project to produce a radiation hard version of an Arm, a number cruncher capable of hosting an operating system.