0effaa9f7e
Add a table comparing the features of all aic7xxx chips. Clean up the discussion of SCB paging. Reviewed by: Kenneth Merry <ken@FreeBSD.org>
250 lines
8.2 KiB
Groff
250 lines
8.2 KiB
Groff
.\"
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.\" Copyright (c) 1995, 1996, 1997, 1998
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.\" Justin T. Gibbs. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software withough specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $Id: ahc.4,v 1.12 1998/06/13 19:06:49 steve Exp $
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.\"
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.Dd October 15, 1998
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.Dt AHC 4 i386
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.Os FreeBSD
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.Sh NAME
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.Nm ahc
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.Nd Adaptec VL/EISA/PCI SCSI host adapter driver
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.Sh SYNOPSIS
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For one or more VL/EISA cards:
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.Cd controller eisa0
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.Cd controller ahc0
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.Pp
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For one or more PCI cards:
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.Cd controller pci0
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.Cd controller ahc0
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.Pp
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To allow PCI adapters to use memory mapped I/O if enabled:
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.Cd options AHC_ALLOW_MEMIO
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.Pp
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For one or more SCSI busses:
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.Cd controller scbus0 at ahc0
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.Sh DESCRIPTION
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This driver provides access to the
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.Tn SCSI
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bus(es) connected to Adaptec
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.Tn AIC7770,
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.Tn AIC7850,
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.Tn AIC7860,
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.Tn AIC7870,
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.Tn AIC7880,
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.Tn AIC7890,
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.Tn AIC7891,
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.Tn AIC7895,
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.Tn AIC7896,
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or
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.Tn AIC7897
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host adapter chips.
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These chips are found on many motherboards as well as the following
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Adaptec SCSI controller cards:
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.Tn 274X(W),
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.Tn 274X(T),
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.Tn 284X,
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.Tn 2920C,
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.Tn 2940,
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.Tn 2940U,
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.Tn 2940AU,
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.Tn 2940UW,
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.Tn 2940UW Dual,
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.Tn 2940U2W,
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.Tn 2940U2B,
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.Tn 2950U2W,
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.Tn 2950U2B,
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.Tn 3940,
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.Tn 3940U,
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.Tn 3940AU,
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.Tn 3940UW,
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.Tn 3940AUW,
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.Tn 3940U2W,
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and
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.Tn 3985.
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.Pp
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Driver features include support for twin and wide busses,
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fast, ultra and ultra2 synchronous transfers depending on controller type,
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tagged queueing,
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and SCB paging.
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.Pp
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Memory mapped I/O can be enabled for PCI devices with the
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.Dq Dv AHC_ALLOW_MEMIO
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configuration option.
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Memory mapped I/O is more efficient than the alternative, programmed I/O.
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Most PCI BIOSes will map devices so that either technique for communicating
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with the card is available.
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In some cases,
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usually when the PCI device is sitting behind a PCI->PCI bridge,
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the BIOS fails to properly initialize the chip for memory mapped I/O.
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The symptom of this problem is usually a system hang if memory mapped I/O
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is attempted.
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Most modern motherboards perform the initialization correctly and work fine
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with this option enabled.
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.Pp
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Per target configuration performed in the
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.Tn SCSI-Select
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menu, accessible at boot
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in
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.No non- Ns Tn EISA
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models,
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or through an
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.Tn EISA
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configuration utility for
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.Tn EISA
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models,
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is honored by this driver with the stipulation that the
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.Tn BIOS
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must be enabled for
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.Tn EISA
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adaptors. This includes synchronous/asynchronous transfers,
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maximum synchronous negotiation rate,
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disconnection,
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the host adapter's SCSI ID,
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and,
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in the case of
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.Tn EISA
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Twin Channel controllers,
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the primary channel selection.
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.Pp
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Note that I/O addresses are determined automatically by the probe routines,
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but care should be taken when using a 284x
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.Pq Tn VESA No local bus controller
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in an
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.Tn EISA
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system. Ensure that the jumpers setting the I/O area for the 284x match the
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.Tn EISA
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slot into which the card is inserted to prevent conflicts with other
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.Tn EISA
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cards.
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.Pp
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Performance and feature sets vary throughout the aic7xxx product line.
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The following table provides a comparison of the different chips supported
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by the
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.Nm
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driver. Note that wide and twin channel features, although always supported
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by a particular chip, may be disabled in a particular motherboard or card
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design.
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.Pp
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.Bd -filled -offset indent
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.Bl -column "aic7770 " "10 " "EISA/VL " "10MHz " "16bit " "SCBs " Features
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.Em "Chip MIPS Bus MaxSync MaxWidth SCBs Features"
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aic7770 10 EISA/VL 10MHz 16Bit 4 1
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aic7850 10 PCI/32 10MHz 8Bit 3
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aic7860 10 PCI/32 20MHz 8Bit 3
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aic7870 10 PCI/32 10MHz 16Bit 16
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aic7880 10 PCI/32 20MHz 16Bit 16
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aic7890 20 PCI/32 40MHz 16Bit 16 3 4 5 6 7
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aic7891 20 PCI/64 40MHz 16Bit 16 3 4 5 6 7
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aic7895 15 PCI/32 20MHz 16Bit 16 2 3 4 5
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aic7896 20 PCI/32 40MHz 16Bit 16 2 3 4 5 6 7
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aic7897 20 PCI/64 40MHz 16Bit 16 2 3 4 5 6 7
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.El
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.Pp
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.Bl -enum -compact
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.It
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Multiplexed Twin Channel Device - One controller servicing two busses.
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.It
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Multi-function Twin Channel Device - Two controllers on one chip.
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.It
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Command Channel Secondary DMA Engine - Allows scatter gather list and
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SCB prefetch.
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.It
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64 Byte SCB Support - SCSI CDB is embedded in the SCB to eliminate an extra DMA.
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.It
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Block Move Instruction Support - Doubles the speed of certain sequencer
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operations.
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.It
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.Sq Bayonet
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style Scatter Gather Engine - Improves S/G prefetch performance.
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.It
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Queueing Registers - Allows queueing of new transactions without pausing the
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sequencer.
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.El
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.Ed
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.Pp
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.Sh SCSI CONTROL BLOCKS (SCBs)
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Every transaction sent to a device on the SCSI bus is assigned a
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.Sq SCSI Control Block
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(SCB). The SCB contains all of the information required by the
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controller to process a transaction. The chip feature table lists
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the number of SCBs that can be stored in on chip memory. All chips
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with model numbers greater than or equal to 7870 allow for the on chip
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SCB space to be augmented with external SRAM up to a maximum of 255 SCBs.
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Very few Adaptec controller have external SRAM.
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If external SRAM is not available, SCBs are a limited resource and
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using them in a straight forward manner would only allow us to
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keep as many transactions as there are SCBs outstanding at a time.
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This would not allow enough concurrency to fully utilize the SCSI
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bus and it's devices. The solution to this problem is
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.Em SCB Paging ,
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a concept similar to memory paging. SCB paging takes advantage of
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the fact that devices usually disconnect from the SCSI bus for long
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periods of time without talking to the controller. The SCBs
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for disconnected transactions are only of use to the controller
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when the transfer is resumed. When the host queues another transaction
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for the controller to execute, the controller firmware will use a
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free SCB if one is available. Otherwise, the state of the most recently
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disconnected (and therefor most likely to stay disconnected) SCB is
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saved, via dma, to host memory, and the local SCB reused to start
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the new transaction. This allows the controller to queue up to
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255 transactions regardless of the amount of SCB space. Since the
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local SCB space serves as a cache for disconnected transactions, the
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more SCB space available, the less host bus traffic consumed saving
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and restoring SCB data.
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.Sh BUGS
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Some Quantum drives (at least the Empire 2100 and 1080s) will not run on an
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.Tn AIC7870
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Rev B in synchronous mode at 10MHz. Controllers with this problem have a
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42 MHz clock crystal on them and run slightly above 10MHz. This confuses
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the drive and hangs the bus. Setting a maximum synchronous negotiation rate
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of 8MHz in the
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.Tn SCSI-Select
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utility
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will allow normal operation.
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.Sh SEE ALSO
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.Xr aha 4 ,
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.Xr ahb 4 ,
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.Xr cd 4 ,
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.Xr scsi 4 ,
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.Xr da 4 ,
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.Xr sa 4
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.Sh AUTHORS
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The
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.Nm
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driver, the
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.Tn AIC7xxx
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sequencer-code assember,
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and the firmware running on the aic7xxx chips was written by
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.An Justin T. Gibbs .
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.Sh HISTORY
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The
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.Nm
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driver appeared in
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.Fx 2.0 .
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