ref: 8f1eb1ac77640d9cd189c49fe48af8cde65eceb1 dir: /sys/src/9/ppc/msaturn.h/
enum { Vecuart0 = 1, Vecuart1 = Vecuart0 + 1, Vectimer0 = 0, Vecether = 3, Vecunused = 15, };