ref: 51f76ae999813bdbf33b06bb4e6c6c8b00f4aec8 dir: /sys/src/9/ppc/msaturn.h/
enum { Vecuart0 = 1, Vecuart1 = Vecuart0 + 1, Vectimer0 = 0, Vecether = 3, Vecunused = 15, };