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NetBSD 6.1.5 - man page for ahc (netbsd section 4)

AHC(4)				   BSD Kernel Interfaces Manual 			   AHC(4)

NAME
     ahc -- Adaptec VL/EISA/PCI/CardBus SCSI host adapter driver

SYNOPSIS
     For VL cards:
     ahc0 at isa? port ? irq ?

     For EISA cards:
     ahc* at eisa? slot ?

     For PCI cards:
     ahc* at pci? dev ? function ?

     For CardBus cards:
     ahc* at cardbus? function ?

     To allow PCI adapters to use memory mapped I/O if enabled:
     options AHC_ALLOW_MEMIO

     Disable tagged queuing (avoids hangs on some hardware under load)
     options AHC_NO_TAGS

     Change the default SCSI id for cards without a SEEPROM (default 7):
     options AHC_CARDBUS_DEFAULT_SCSI_ID=integer

     For SCSI buses:
     scsibus* at ahc?

DESCRIPTION
     The ahc device driver supports SCSI controllers based on Adaptec AIC77xx and AIC78xx SCSI
     host adapter chips found on many motherboards as well as Adaptec SCSI controller cards.

     Driver features include support for twin and wide buses, fast, ultra or ultra2 synchronous
     transfers depending on controller type, tagged queuing and SCB paging.

     Memory mapped I/O can be enabled for PCI devices with the ``AHC_ALLOW_MEMIO'' configuration
     option.  Memory mapped I/O is more efficient than the alternative, programmed I/O.  Most PCI
     BIOSes will map devices so that either technique for communicating with the card is avail-
     able.  In some cases, usually when the PCI device is sitting behind a PCI->PCI bridge, the
     BIOS may fail to properly initialize the chip for memory mapped I/O.  The typical symptom of
     this problem is a system hang if memory mapped I/O is attempted.  Most modern motherboards
     perform the initialization correctly and work fine with this option enabled.

     Per target configuration performed in the SCSI-Select menu, accessible at boot in non-EISA
     models, or through an EISA configuration utility for EISA models, is honored by this driver.
     This includes synchronous/asynchronous transfers, maximum synchronous negotiation rate, wide
     transfers, disconnection, the host adapter's SCSI ID, and, in the case of EISA Twin Channel
     controllers, the primary channel selection.  For systems that store non-volatile settings in
     a system specific manner rather than a serial EEPROM directly connected to the aic7xxx con-
     troller, the BIOS must be enabled for the driver to access this information.  This restric-
     tion applies to all EISA and many motherboard configurations.

     Note that I/O addresses are determined automatically by the probe routines, but care should
     be taken when using a 284x (VESA local bus controller) in an EISA system.	The jumpers set-
     ting the I/O area for the 284x should match the EISA slot into which the card is inserted to
     prevent conflicts with other EISA cards.

     Performance and feature sets vary throughout the aic7xxx product line.  The following table
     provides a comparison of the different chips supported by the ahc driver.	Note that wide
     and twin channel features, although always supported by a particular chip, may be disabled
     in a particular motherboard or card design.

     Chip     MIPS Bus	   MaxSync MaxWidth SCBs Features
     aic7770  10   EISA/VL 10MHz   16Bit    4	 1
     aic7850  10   PCI/32  10MHz   8Bit     3
     aic7860  10   PCI/32  20MHz   8Bit     3
     aic7870  10   PCI/32  10MHz   16Bit    16
     aic7880  10   PCI/32  20MHz   16Bit    16
     aic7890  20   PCI/32  40MHz   16Bit    16	 3 4 5 6 7 8
     aic7891  20   PCI/64  40MHz   16Bit    16	 3 4 5 6 7 8
     aic7892  20   PCI/64  80MHz   16Bit    16	 3 4 5 6 7 8
     aic7895  15   PCI/32  20MHz   16Bit    16	 2 3 4 5
     aic7895C 15   PCI/32  20MHz   16Bit    16	 2 3 4 5 8
     aic7896  20   PCI/32  40MHz   16Bit    16	 2 3 4 5 6 7 8
     aic7897  20   PCI/64  40MHz   16Bit    16	 2 3 4 5 6 7 8
     aic7899  20   PCI/64  80MHz   16Bit    16	 2 3 4 5 6 7 8

     1.   Multiplexed Twin Channel Device - One controller servicing two buses.
     2.   Multi-function Twin Channel Device - Two controllers on one chip.
     3.   Command Channel Secondary DMA Engine - Allows scatter gather list and SCB prefetch.
     4.   64 Byte SCB Support - SCSI CDB is embedded in the SCB to eliminate an extra DMA.
     5.   Block Move Instruction Support - Doubles the speed of certain sequencer operations.
     6.   'Bayonet' style Scatter Gather Engine - Improves S/G prefetch performance.
     7.   Queuing Registers - Allows queuing of new transactions without pausing the sequencer.
     8.   Multiple Target IDs - Allows the controller to respond to selection as a target on mul-
	  tiple SCSI IDs.

HARDWARE
     Supported SCSI controllers include:

	   Adaptec AHA-2742W EISA Fast Wide SCSI adapter

	   Adaptec AHA-274xAT EISA dual channel Fast SCSI adapter

	   Adaptec AHA-284x VL Fast SCSI adapter

	   Adaptec AHA-2910 PCI Fast SCSI adapter (no SCSI BIOS)

	   Adaptec AHA-2915 PCI Fast SCSI adapter (no SCSI BIOS)

	   Adaptec AHA-2920C PCI Fast SCSI adapter

		 Note: Adaptec AHA-2920/A which use the Future Domain's chips are not supported
		 by this driver.

	   Adaptec AHA-2930C PCI Ultra SCSI adapter

	   Adaptec AHA-2930U2 PCI Ultra2 Wide LVD SCSI adapter

	   Adaptec AHA-2940 PCI Fast SCSI adapter

	   Adaptec AHA-2940U PCI Ultra SCSI adapter

	   Adaptec AHA-2940AU PCI Ultra SCSI adapter

	   Adaptec AHA-2940UW PCI Ultra Wide SCSI adapter

	   Adaptec AHA-2940UW Dual PCI dual channel Ultra Wide SCSI adapter

	   Adaptec AHA-2940UW Pro PCI Ultra Wide SCSI adapter

	   Adaptec AHA-2940U2W PCI Ultra2 Wide LVD SCSI adapter

	   Adaptec AHA-2940U2B PCI Ultra2 Wide LVD SCSI adapter

	   Adaptec AHA-2944W PCI Fast Wide Differential SCSI adapter

	   Adaptec AHA-2944UW PCI Ultra Wide Differential SCSI adapter

	   Adaptec AHA-2950U2W

	   Adaptec AHA-2950U2B 64bit PCI Ultra2 Wide LVD SCSI adapter

	   Adaptec AHA-19160B PCI Ultra160 Wide LVD SCSI adapter

	   Adaptec ASC-29160 PCI Ultra160 Wide LVD SCSI adapter

	   Adaptec AHA-29160N PCI Ultra160 Wide LVD SCSI adapter

	   Adaptec AHA-29160B 64bit PCI Ultra160 Wide LVD SCSI adapter

	   Adaptec AHA-3940 PCI dual channel Fast SCSI adapter

	   Adaptec AHA-3940U PCI dual channel Ultra SCSI adapter

	   Adaptec AHA-3940AU PCI dual channel Ultra SCSI adapter

	   Adaptec AHA-3940UW PCI dual channel Ultra Wide SCSI adapter

	   Adaptec AHA-3940AUW PCI dual channel Ultra Wide SCSI adapter

	   Adaptec AHA-3940U2W PCI dual channel Ultra2 Wide LVD SCSI adapter

	   Adaptec AHA-3950U2 64bit PCI dual channel Ultra2 Wide LVD SCSI adapter

	   Adaptec AHA-3960 64bit PCI dual channel Ultra160 Wide LVD SCSI adapter

	   Adaptec AHA-3985 PCI dual channel Fast SCSI RAID adapter

	   Adaptec AHA-39160 64bit PCI dual channel Ultra160 Wide LVD SCSI adapter

	   Adaptec AHA-4944UW PCI quad channel PCI Ultra Wide Differential SCSI adapter

	   Other SCSI controllers based on the Adaptec AIC7770, AIC7850, AIC7860, AIC7870,
	   AIC7880, AIC7890, AIC7891, AIC7892, AIC7895, AIC7896, AIC7897 and AIC7899 SCSI host
	   adapter chips.

SCSI CONTROL BLOCKS (SCBs)
     Every transaction sent to a device on the SCSI bus is assigned a 'SCSI Control Block' (SCB).
     The SCB contains all of the information required by the controller to process a transaction.
     The chip feature table lists the number of SCBs that can be stored in on-chip memory.  All
     chips with model numbers greater than or equal to 7870 allow for the on chip SCB space to be
     augmented with external SRAM up to a maximum of 255 SCBs.	Very few Adaptec controller con-
     figurations have external SRAM.

     If external SRAM is not available, SCBs are a limited resource.  Using the SCBs in a
     straight forward manner would only allow the driver to handle as many concurrent transac-
     tions as there are physical SCBs.	To fully use the SCSI bus and the devices on it, requires
     much more concurrency.  The solution to this problem is SCB Paging, a concept similar to
     memory paging.  SCB paging takes advantage of the fact that devices usually disconnect from
     the SCSI bus for long periods of time without talking to the controller.  The SCBs for dis-
     connected transactions are only of use to the controller when the transfer is resumed.  When
     the host queues another transaction for the controller to execute, the controller firmware
     will use a free SCB if one is available.  Otherwise, the state of the most recently discon-
     nected (and therefor most likely to stay disconnected) SCB is saved, via DMA, to host mem-
     ory, and the local SCB reused to start the new transaction.  This allows the controller to
     queue up to 255 transactions regardless of the amount of SCB space.  Since the local SCB
     space serves as a cache for disconnected transactions, the more SCB space available, the
     less host bus traffic consumed saving and restoring SCB data.

SEE ALSO
     aha(4), ahb(4), ahd(4), cd(4), ch(4), intro(4), scsi(4), sd(4), st(4)

HISTORY
     The ahc driver appeared in FreeBSD 2.0 and NetBSD 1.1.

AUTHORS
     The ahc driver, the AIC7xxx sequencer-code assembler, and the firmware running on the
     aic7xxx chips was written by Justin T. Gibbs.  NetBSD porting is done by Stefan Grefen,
     Charles M. Hannum, Michael Graff, Jason R. Thorpe, Pete Bentley, Frank van der Linden and
     Noriyuki Soda.

BUGS
     Some Quantum drives (at least the Empire 2100 and 1080s) will not run on an 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.  This confuses the drive and hangs the bus.  Setting a
     maximum synchronous negotiation rate of 8MHz in the SCSI-Select utility will allow normal
     operation.

     Target mode is not supported on NetBSD version of this driver.

BSD					  July 16, 2007 				      BSD


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