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     sym — NCR/Symbios/LSI Logic 53C8XX PCI SCSI host adapter driver


     To compile this driver into the kernel, place the following lines in your kernel
     configuration file:

           device pci
           device scbus
           device sym

           To disable PCI parity checking (needed for broken bridges):
           options SYM_SETUP_PCI_PARITY=<boolean>

           To control driver probing against HVD buses:
           options SYM_SETUP_SCSI_DIFF=<bit combination>

           To control chip attachment balancing between the ncr driver and this driver:
           options SYM_SETUP_LP_PROBE_MAP=<bit combination>

     Alternatively, to load the driver as a module at boot time, place the following line in



     This driver provides support for the Symbios/LSI Logic 53C8XX PCI SCSI controllers.

     Driver features include support for wide SCSI busses and fast10, fast20, fast40 and
     fast80-dt synchronous data transfers depending on controller capabilities.  It also provides
     generic SCSI features such as tagged command queueing and auto-request sense.  This driver
     is configured by default for a maximum of 446 outstanding commands per bus, 8 LUNs per
     target and 64 tagged tasks per LUN.  These numbers are not so much limited by design as they
     are considered reasonable values for current SCSI technology.  These values can be increased
     by changing appropriate constants in driver header files (not recommended).

     This driver supports the entire Symbios 53C8XX family of PCI SCSI controllers.  It also
     offers the advantage of architectural improvements available only with newer chips.

     sym notably handles phase mismatch from SCRIPTS for the 53C896, 53C895A, and 53C1010 cores.
     As a result, it guarantees that no more than 1 interrupt per IO completion is delivered to
     the CPU, and that the SCRIPTS processor is never stalled waiting for CPU attention in normal

     sym also uses LOAD/STORE SCRIPTS instructions for chips that support it.  Only the early
     810, 815 and 825 NCR chips do not support LOAD/STORE.  Use of LOAD/STORE instead of MEMORY
     MOVE allows SCRIPTS to access IO registers internal to the chip (no external PCI cycles).
     As a result, the driver guarantees that no PCI self-mastering will occur for chips that
     support LOAD/STORE.

     LOAD/STORE instructions are also faster than MEMORY MOVE because they do not involve the
     chip DMA FIFO and are coded on 2 DWORDs instead of 3.

     For the early NCR 810, 815 and 825 chips, the driver uses a separate SCRIPTS set that uses
     MEMORY MOVE instructions for data movements.  This is because LOAD/STORE are not supported
     by these chips.

     HVD/LVD capable controllers (895, 895A, 896, and 897) report the actual bus mode in the
     STEST4 chip IO registers.  This feature allows the driver to safely probe against bus mode
     and to set up the chip accordingly.  By default the driver only supports HVD for these
     chips.  For other chips that can support HVD but not LVD, the driver has to probe
     implementation dependent registers (GPIO) in order to detect HVD bus mode.  Only HVD
     implementations that conform with Symbios Logic recommendations can be detected by the
     driver.  When the SYM_SETUP_SCSI_DIFF kernel option is assigned a value of 1, the driver
     will also probe against HVD for 825a, 875, 876 and 885 chips, assuming Symbios Logic
     compatible implementation of HVD.

     When the SYM_SETUP_PCI_PARITY is assigned a value of 0, the driver will not enable PCI
     parity checking for 53C8XX devices.  PCI parity checking should not be an option for PCI
     SCSI controllers, but some systems have been reported to fail using 53C8XX chips, due to
     spurious or permanent PCI parity errors detected.  This option is supplied for convenience
     but it is neither recommended nor supported.

     The generic ncr(4) driver also supports SYM53C8XX based PCI SCSI controllers, except for the
     SYM53C1010, which is only supported by the sym driver.

     By default, when both the ncr(4) and sym drivers are configured, the sym driver takes
     precedence over the ncr(4) driver.  The user can indicate a balancing of chip types between
     the two drivers by defining the SYM_SETUP_LP_PROBE_MAP kernel configuration option as

     Bit     Devices to be attached by ncr instead
     0x01    53C810a, 53C860
     0x02    53C825a, 53C875, 53C876, 53C885, 53C895
     0x04    53C895a, 53C896, 53C897, 53C1510d
     0x40    53C810, 53C815, 53C825

     For example, if SYM_SETUP_LP_PROBE_MAP is supplied with the value 0x41, the ncr(4) driver
     will attach to 53C810, 53C815, 53C825, 53C810a, and 53C860 based controllers, and the sym
     driver will attach to all other 53C8XX based controllers.

     When only the sym driver is configured, the SYM_SETUP_LP_PROBE_MAP option has no effect.
     Thus, in this case, the sym driver will attach all 53C8XX based controllers present in the

     This driver offers other options that are not currently exported to the user.  They are
     defined and documented in the sym_conf.h driver file.  Changing these options is not
     recommended unless absolutely necessary.  Some of these options are planned to be exported
     through sysctl(3) or an equivalent mechanism in a future driver releases and therefore, no
     compatibility is guaranteed.

     At initialization, the driver tries to detect and read user settings from controller NVRAM.
     The Symbios/Logic NVRAM layout and the Tekram NVRAM layout are currently supported.  If the
     reading of the NVRAM succeeds, the following settings are taken into account and reported to

     Host settings           Symbios    Tekram
     SCSI parity checking    Y          N
     Host SCSI ident         Y          Y
     Verbose messages        Y          N
     Scan targets hi-lo      Y          N
     Avoid SCSI bus reset    Y          N

     Device settings       Symbios    Tekram
     Synchronous period    Y          Y
     SCSI bus width        Y          Y
     Queue tag enable      Y          Y
     Number of tags        NA         Y
     Disconnect enable     Y          Y
     Scan at boot time     Y          N
     Scan LUN              Y          N

     Devices that are configured as disabled for 'scan' in the NVRAM are not reported to CAM at
     system start-up.  They can be discovered later using the ‘camcontrol rescan’ command.

     The table below summarizes the main features and capabilities of the NCR/Symbios/LSI Logic
     53C8XX family of PCI SCSI controllers.

     Chip          Sync    Width   SRAM   PCI64   Supported
     sym53c810     10MHz   8Bit    N      N       Y
     sym53c810a    10MHz   8Bit    N      N       Y
     sym53c815     10MHz   8Bit    N      N       Y
     sym53c825     10MHz   16Bit   N      N       Y
     sym53c825a    10MHz   16Bit   4KB    N       Y
     sym53c860     20MHz   8Bit    N      N       Y
     sym53c875     20MHz   16Bit   4KB    N       Y
     sym53c876     20MHz   16Bit   4KB    N       Y
     sym53c885     20MHz   16Bit   4KB    N       Y
     sym53c895     40MHz   16Bit   4KB    N       Y
     sym53c895A    40MHz   16Bit   8KB    N       Y
     sym53c896     40MHz   16Bit   8KB    Y       Y
     sym53c897     40MHz   16Bit   8KB    Y       Y
     sym53c1510D   40MHz   16Bit   4KB    Y       Y
     sym53c1010    80MHz   16Bit   8KB    Y       Y


     The sym driver provides support for the following Symbios/LSI Logic PCI SCSI controllers:


     The SCSI controllers supported by sym can be either embedded on a motherboard, or on one of
     the following add-on boards:

        ASUS SC-200, SC-896
        Data Technology DTC3130 (all variants)
        DawiControl DC2976UW
        Diamond FirePort (all)
        NCR cards (all)
        Symbios cards (all)
        Tekram DC390W, 390U, 390F, 390U2B, 390U2W, 390U3D, and 390U3W
        Tyan S1365


     The DEC KZPCA-AA is a rebadged SYM8952U.


     cd(4), da(4), ncr(4), sa(4), scsi(4), camcontrol(8)


     The sym driver appeared in FreeBSD 4.0.


     The sym driver was written by Gerard Roudier and is derived from the Linux sym53c8xx driver
     from the same author.  The sym53c8xx driver is derived from the ncr53c8xx driver, which was
     ported from the FreeBSD ncr(4) driver to Linux-1.2.13.  The original ncr(4) driver was
     written for 386BSD and FreeBSD by Wolfgang Stanglmeier and Stefan Esser.


     No known bugs.