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WD(4) NetBSD Kernel Interfaces Manual WD(4)
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by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
wd -- WD100x compatible hard disk driver
wd* at atabus? drive ? flags 0x0000
wd* at umass?
The wd driver supports hard disks that emulate the Western Digital
WD100x. This includes standard MFM, RLL, ESDI, IDE, EIDE, and SATA
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:
Whether to use NCQ ATA commands for the disk. Only effective
when the disk hardware actually claims to support NCQ. Default
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.
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:
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.
ata(4), intro(4), pciide(4), scsi(4), umass(4), wdc(4), atactl(8),
The optional software bad sector list does not interoperate well with
sector remapping features of modern disks. To let the disk remap a sec-
tor internally, the software bad sector list must be flushed or disabled
NetBSD 9.99 January 13, 2020 NetBSD 9.99