.\"	$NetBSD: ahc.4,v 1.1.2.1 1996/08/25 17:22:14 thorpej Exp $
.\"
.\" Copyright (c) 1995, 1996 
.\" 	Justin T. Gibbs.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. The name of the author may not be used to endorse or promote products
.\"    derived from this software withough specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
.Dd April 20, 1996
.\".Dt AHC 4 i386
.\".Os FreeBSD
.Dt AHC 4
.Os
.Sh NAME
.Nm ahc
.Nd Adaptec VL/EISA/PCI SCSI host adapter driver
.Sh SYNOPSIS
.ie 0 \{
For one or more VL/EISA cards:
.Cd controller eisa0
.Cd controller ahc0
\}
\{For VL cards:
.Cd ahc0	at isa? port ? irq ?
.Pp
For EISA cards:
.Cd ahc*	at eisa? slot ?\}
.Pp
.ie 0 \{
For one or more PCI cards:
.Cd controller pci0
.Cd controller ahc0
\}
\{For PCI cards:
.Cd ahc*	at pci? dev ? function ?\}
.Pp
To enable tagged queueing:
.Cd options AHC_TAGENABLE
.Pp
To enable SCB paging:
.Cd options AHC_SCBPAGING_ENABLE
.Pp
.ie 0 \{
For one or more SCSI busses:
.Cd controller scbus0 at ahc0
\}
\{For SCSI busses:
.Cd scsibus* at ahc?\}
.Sh DESCRIPTION
This driver provides access to the
.Tn SCSI
bus connected to an Adaptec 
274x, 284x, 2940, 3940, or controllers based on the
.Tn AIC7770,
.Tn AIC7850,
.Tn AIC7860,
.Tn AIC7870,
or
.Tn AIC7880
host adapter chips.
Features include support for twin and wide busses,
ultra
.Tn SCSI,
two active commands at a time per non-tagged queueing target,
tagged queuing,
and SCB paging which allows up to 255 active commands on all adapters
except those using 
.Tn AIC7770
chips prior to revision E.
Tagged queueing is enabled with the
.Dq Dv AHC_TAGENABLE
configuration option.
SCB paging is enabled with the
.Dq Dv AHC_SCBPAGING_ENABLE
configuration option.
.Pp
Per target configuration performed in the 
.Tn SCSI-Select
menu, accesible at boot
in 
.No non- Ns Tn EISA
models or through an 
.Tn EISA
configuration utility for 
.Tn EISA
models,
is honored by this driver with the stipulation that the 
.Tn BIOS
must be enabled for 
.Tn EISA
adaptors.  This includes synchronous/asynchronous transfers,
maximum synchronous negotiation rate,
disconnection,
and the host adapter's SCSI ID.
.Pp
Note that I/O addresses are determined automatically by the probe routines,
but care should be taken when using a 284x
.Pq Tn VESA No local bus controller
in an
.Tn EISA 
system.  Ensure that the jumpers setting the I/O area for the 284x match the 
.Tn EISA
slot into which the card is inserted to prevent conflicts with other
.Tn EISA
cards.
.Sh BUGS
Some Quantum drives (at least the Empire 2100 and 1080s) will not run on an
.Tn AIC7870
Rev B in synchronous mode at 10MHz.  Controllers with this problem have a
42 MHz clock crystal on them and run slightly above 10MHz, causing the
drive much confusion.  Setting a maximum synchronous negotiation rate of 8MHz
in the 
.Tn SCSI-Select
utility
will allow normal function.
.if 1 \{
.Pp
There are four problems known this version of this driver as follows.
All of these problems relate to MI SCSI system.
.Pp
Cannot handle SCSI ID greater than 7 with WIDE SCSI adapter.
.Pp
It is dangerous to simultaneously access SCSI devices more than half
number of SCBs. It may cause fatal disk trouble. In this case,
diagnostics message 
.Dq not queued, error ...
is displayed to console.
For example, AHA-274x and AHA-284x have only 4 SCBs, so that using 3 SCSI
devices is dangerous, using 2 devices is OK.
.Pp
When you suddenly access SCSI devices on free physical memory shortage
conditions, and if there have been very few load on SCSI devices until 
then, it may cause fatal disk trouble. In this case, diagnostics
message 
.Dq ahc0: Can't malloc SCB
and 
.Dq not queued, error ...
is displayed to console.
.Pp
SCSI residual handling is not complete.
\}
.Sh SEE ALSO
.Xr aha 4 ,
.Xr ahb 4
.if 0 \{
.Xr cd 4 ,
.Xr scsi 4 ,
.Xr sd 4 ,
.Xr st 4
\}
.Sh AUTHOR
The
.Nm
driver was written by Justin Gibbs.  The
.Tn AIC7xxx
sequencer-code assembler was
written by John Aycock.