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.\" Copyright (c) 1994 Wilko Bulte
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.\" $FreeBSD$
.\"
.Dd July 4, 2004
.Dt AHB 4
.Os
.Sh NAME
.Nm ahb
.Nd Adaptec EISA SCSI host adapter driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device scbus"
.Cd "device ahb"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
ahb_load="YES"
.Ed
.Sh DESCRIPTION
This driver provides access to the
.Tn SCSI
bus connected to an Adaptec
AHA-174X host adapters in
.Dq Em enhanced
mode.
Tagged queueing and synchronous SCSI transfers are supported.
.Sh HARDWARE
The
.Nm
driver supports the following SCSI host adapters:
.Pp
.Bl -bullet -compact
.It
Adaptec AHA-1740
.It
Adaptec AHA-1742
.It
Adaptec AHA-1740A
.It
Adaptec AHA-1742A
.El
.Sh SEE ALSO
.Xr aha 4 ,
.Xr ahc 4 ,
.Xr aic 4 ,
.Xr cd 4 ,
.Xr da 4 ,
.Xr sa 4 ,
.Xr scsi 4
.Sh AUTHORS
The
.Nm
driver was written by
.An Justin T. Gibbs .
.Sh 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.