gio —
SGI's Graphics I/O (GIO) bus (an early PCI-like bus)
gio0 at imc0
gio0 at pic0
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
  sgimips/hpc(4)
  peripheral controller, and memory and CPU are accessed through the
  sgimips/imc(4) (Indy
  Memory Controller) or
  sgimips/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.
The gio driver first appeared in NetBSD
  1.5.
Challenge S systems may use only one gio DMA-capable
  expansion card, despite having two slots. Cards based on the
  sgimips/hpc(4)
  controller, such as the GIO32 scsi and E++ Ethernet adapters, must be placed
  in slot 1 (closest to the side of the case). All other cards must be placed in
  slot 0 (adjacent to the memory banks).
Indigo2 and Challenge M systems contain either three or four GIO64
    connectors, depending on the model. However, in both cases only two
    electrically distinct slots are present. Therefore, distinct expansion cards
    may not share physical connectors associated with the same slot. Refer to
    the PCB stencils to determine the association between physical connectors
    and slots.
Systems employing the
  sgimips/imc(4) may
  experience spurious SysAD bus parity errors when using expansion cards, which
  do not drive all data lines during a CPU PIO read. The only workaround is to
  disable SysAD parity checking when using such cards.