.\"
.\" Copyright (c) 1994 Wilko Bulte
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.Dd January 19, 1996
.Dt AHB 4 i386
.Os FreeBSD
.Sh NAME
.Nm ahb
.Nd Adaptec EISA SCSI host adapter driver
.Sh SYNOPSIS
.Cd controller ahb0
.Cd controller scbus0 at ahb0
.Sh DESCRIPTION
This driver provides access to the
.Tn SCSI
bus connected to an Adaptec 
174x hostadapter in either 
.Dq Em standard
or
.Dq Em enhanced
mode. If the controller
is set to standard mode (using the
.Tn EISA
configuration utility),
the driver will automatically 
switch the card to enhanced mode during the device probe.
.Pp
.Sy N.B. :
When configuring a system
with both
.Xr aha 4
and
.Nm
drivers, the
.Nm
driver should be listed first in the kernel configuration file.  This
ensures that the
.Nm
driver will find the Adaptec 174x boards before the 
.Xr aha 4
driver probes for Adaptec 154x boards.
.Pp
Note that no I/O addresses are configured in the kernel config file. The
174x uses
.Tn EISA
slot-specific I/O which is configured automatically.
.\"
.\" .Sh DIAGNOSTICS
.\"
.Sh SEE ALSO
.Xr aha 4 ,
.Xr ahc 4 ,
.Xr cd 4 ,
.Xr scsi 4 ,
.Xr sd 4 ,
.Xr st 4
.Sh AUTHOR
The
.Nm
driver was written by Julian Elischer for
.Tn Mach
2.5.  It was converted to automatic
.Tn EISA
configuration by Justin Gibbs.
.Sh HISTORY
The
.Nm
driver first appeared in the
.Tn 386BSD
patchkit.