AHC(4)

NAME
ahc - Adaptec VL/EISA/PCI SCSI host adapter driver

SYNOPSIS
For VL/EISA cards:
controller ahc0 at isa? bio irq? vector ahcintr

For PCI cards:
controller ahc0

To enable tagged queueing:
options AHC_TAGENABLE

For one or more SCSI busses:
controller scbus0 at ahc0

DESCRIPTION
This driver provides access to the SCSI bus connected to an Adaptec 274x, 284x, 294x, or motherboard-based AIC7770 or AIC7870 host adapter. Features include twin and wide bus support, two commands per target in non-tagged-queuing mode, and experimental tagged queuing support enabled with the “AHC_TAGENABLE” configuration option.

Per target configuration performed in the SCSI-Select menu, accesible at boot in non-EISA models or through an EISA configuration utility for EISA models, is honored by this driver with the stipulation that the BIOS must be enabled for EISA adaptors. This includes synchronous/asynchronous transfers, disconnection, and maximum synchronous negotiation rate settings.

Note that I/O addresses are determined automatically by the probe routines, but care should be taken when using a 284x (VESA local bus controller) in an EISA system. Ensure that the jumpers setting the I/O area for the 284x match the EISA slot into which the card is inserted to prevent conflicts with other EISA cards.

BUGS
Some Quantum drives (at least the Empire 2100 and 1080s) will not run on an AIC7870 in synchronous mode at 10MB/s. It is speculated that the Adaptec runs slightly above 10MB/s, causing the drive much confusion. Setting a maximum synchronous negotiation rate of 8MB/s in the SCSI-Select utility will allow normal function.

The SCSI ID of AIC7870-based controllers (AHA-294x) is hard coded to 7 by the driver. The user configured ID can be obtained by querying the adapter, but there is no driver support for this as of yet.

SEE ALSO
aha(4), ahb(4), cd(4), scsi(4), sd(4), st(4)

AUTHOR
The ahc driver was written by Justin Gibbs. The AIC7xxx sequencer-code assembler was written by John Aycock.

HISTORY
The ahc driver appeared in FreeBSD 2.1.