He became a licenced physician in 1976 and from 1979 to 1981 he served as District Medical Officer in Nacala in northern Mozambique.

In 1983, she designed the instruction set for one of the first RISC processors, the Acorn RISC Machine (ARM), later to become one of the most successful IP cores (i.e., a licenced CPU core) of the 1990s and 2000s.