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WD(4)                        Device Drivers Manual                       WD(4)

NAME
     wd - WD100x compatible hard disk driver

SYNOPSIS
     wd* at atabus? drive ? flags 0x0000
     wd* at umass?
     options WD_SOFTBADSECT

DESCRIPTION
     The wd driver supports hard disks that emulate the Western Digital
     WD100x.  This includes standard MFM, RLL, ESDI, IDE, EIDE, and SATA
     drives.

     The flags are used only with controllers that support DMA operations and
     mode settings (like some pciide controllers).  The lowest order nibble
     (rightmost digit) of the flags defines the PIO mode, the next four bits
     define the DMA mode and the third nibble defines the UltraDMA mode.  For
     each set of four bits, the 3 lower bits define the mode to use and the
     last bit must be set to 1 for this setting to be used.  For DMA and UDMA,
     0xf (1111) means 'disable'.  For example, a flags value of 0x0fac (1111
     1010 1100) means 'use PIO mode 4, DMA mode 2, disable UltraDMA'.  0x0000
     means "use whatever the drive claims to support."

     The kernel configuration option "options WD_SOFTBADSECT" enables a
     software managed bad-sector list which will prevent further accesses to
     sectors where an unrecoverable read error occurred.  A user interface is
     provided by dkctl(8).  Unlike the (historical) mechanisms provided by
     bad144(8) and badsect(8), the software list supports neither sector
     replacement nor retention across reboots.

     The following sysctl(8) variables control behavior of disks attached
     using this driver:

     hw.wdX.use_ncq
               Whether to use NCQ ATA commands for the disk.  Only effective
               when the disk hardware actually claims to support NCQ.  Default
               to true.

     hw.wdX.use_ncq_prio
               Use optional NCQ priority for high-priority I/O like meta-data.
               Intended only for experimental use right now, might negatively
               affect performance.  This setting only has effect if
               hw.wdX.use_ncq is also true.  Default to false.

NOTES
     Certain Seagate Barracuda drives sold around 2003 have a known firmware
     bug leading to corrupted write transfers for sector counts n*15 + 1, in
     combination with certain ATA controllers, most commonly Silicon Image
     3xxx.  Affected drives include, but are not limited to:

           Seagate ST3120023AS
           Seagate ST380023AS
           Seagate ST360015AS

     If you have one of these drives, it's recommended to replace the drive.
     There used to exist a driver workaround greatly reducing performance, but
     the code was completely removed in NetBSD 8.0.

SEE ALSO
     ata(4), intro(4), pciide(4), scsi(4), umass(4), wdc(4), atactl(8),
     dkctl(8)

BUGS
     The optional software bad sector list does not interoperate well with
     sector remapping features of modern disks.  To let the disk remap a
     sector internally, the software bad sector list must be flushed or
     disabled before.

NetBSD 10.99                   January 13, 2020                   NetBSD 10.99