The
gio bus is a bus for connecting high-speed peripherals to the main memory and CPU. The devices themselves are typically (but not necessarily) connected to the
hpc(4) peripheral controller, and memory and CPU are accessed through the
imc(4) (Indy Memory Controller) or
pic(4) (Processor Interface Controller). The
gio bus is found on the Personal Iris 4D/3x, Indigo, Indy, Challenge S, Challenge M, and Indigo2 machines and exists in three incarnations: GIO32, GIO32-bis, and GIO64.