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IOASIC(4) Device Drivers Manual (alpha) IOASIC(4)

ioasicbaseboard IO control ASIC for DEC TURBOchannel systems

ioasic0 at tc? slot ? offset ?

The ioasic driver provides support for the DEC proprietary IOCTL ASIC found on DEC 3000 TURBOchannel machines.

The ioasic provides hardware DMA channels and interrupt support for several baseboard devices, including one asc(4) SCSI device with a scatter/gather DMA channel, an mc146818-compatible mcclock, an Am7930 audio device bba(4), two zs(4) dual-port serial devices, and an AMD 7990 LANCE le(4) Ethernet interface.

The ioasic is also used for the audio/ISDN hardware on 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.

asc(4), bba(4), intro(4), le(4), zs(4)

The ioasic driver first appeared in NetBSD 1.1, derived from DECstation boot-time configuration code in 4.4BSD.

November 2, 2017 OpenBSD-6.9