NAME

     ahb — Adaptec EISA SCSI host adapter driver

SYNOPSIS

     To compile this driver into the kernel, place the following lines in your kernel
     configuration file:

           device scbus
           device ahb

     Alternatively, to load the driver as a module at boot time, place the following line in
     loader.conf(5):

           ahb_load="YES"

DESCRIPTION

     This driver provides access to the SCSI bus connected to an Adaptec AHA-174X host adapters
     in “enhanced” mode.  Tagged queueing and synchronous SCSI transfers are supported.

HARDWARE

     The ahb driver supports the following SCSI host adapters:

     •   Adaptec AHA-1740
     •   Adaptec AHA-1742
     •   Adaptec AHA-1740A
     •   Adaptec AHA-1742A

SEE ALSO

     aha(4), ahc(4), aic(4), cd(4), da(4), sa(4), scsi(4)

AUTHORS

     The ahb driver was written by Justin T. Gibbs.

CAVEATS

     The Adaptec 174X is very sensitive to SCSI bus termination and cable length.  It may also
     have difficulties operating with some modern devices that, due to their speed, expose timing
     problems in the controller.  There are no known mechanisms for working around device
     incompatibilities of this nature.