The
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
scc 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.