| IOASIC(4) | Device Drivers Manual | IOASIC(4) | 
ioasic —
ioasic0 at tc? slot ? offset ?
ioasic driver provides support for the DEC
  proprietary IOCTL ASIC found on all DEC TURBOchannel machines with MIPS
  (DECstation 5000 series, excluding the 5000/200) and Alpha (3000-series)
  processors. On these machines (including the 5000/200), all baseboard devices
  should be configured as children of the ioasic device.
The ioasic provides hardware DMA channels
    and interrupt support for several baseboard devices, including one
    asc SCSI device with a scatter/gather DMA channel,
    an mc146818-compatible mcclock, an Am7930 audio
    device bba, one or two zs
    two-port serial devices, and a AMD 7990 LANCE le
    Ethernet interface.
The ioasic is also used for the
    floppy-disc drive and audio/ISDN hardware on the Personal DECstation and
    audio-equipped TURBOchannel Alphas, where the ioasic
    hardware provides a scatter-gather DMA channel between the 16-bit device and
    the 32-bit tc DMA address space.
Support for scatter-gather DMA eliminates the need for additional
    copying. A baseboard asc SCSI adaptor attached to an
    ioasic will give slightly better performance than
    its tc counterpart.
ioasic driver first appeared in
  NetBSD 1.1, derived from DECstation boot-time
  configuration code in 4.4BSD.
| September 12, 2007 | NetBSD 10.0 |