Eventually the phone switch was abandoned in favor of a general-purpose processor but not before they stumbled onto the RISC processor which eventually became the IBM 801. As [Paul] explains ...

(Performance Optimization With Enhanced RISC CPU) A family of RISC-based CPUs that use the Power Architecture from IBM. The heart of IBM's midrange computer line (see Power Systems), as well as ...

Much as how the Intel i7 in a top-of-the-line desktop can still run code written for the original IBM PC, the ARM chip ... The Archimedes ran RISC OS, a very nice graphical operating system ...