Unknown ATA chipsets are supported in PIO modes, and if the standard
busmaster DMA registers are present and contain valid setup, DMA is
also enabled, although the max mode is limited to UDMA33, as it is
not known what the chipset can do and how to program it.
driver can change the transfer mode and various other parameters
when the system is up and running.
driver sets the maximum transfer mode supported by the hardware as default.
driver sometimes warns:
``DMA limited to UDMA33, non-ATA66 cable or device.
This means that
driver has detected that the required 80 conductor cable is not present
or could not be detected properly,
or that one of the devices on the channel only accepts up
tunable can be set to 0 to disable this check.
Unknown ATAPI devices are initialized to DMA mode if the
tunable is set to 1 and they support at least UDMA33 transfers.
Otherwise they are set to PIO mode because severe DMA problems are
common even if the device capabilities indicate support.
You can always try to set DMA mode on an ATAPI device using
but be aware that your hardware might
support it and can potentially
the entire system causing data loss.
ATA disk device nodes
ATA RAID device nodes
ATAPI CD-ROM device nodes
ATAPI floppy drive device nodes
ATAPI tape drive device nodes
sample generic kernel config file for
Please remember that in order to use UDMA4/ATA66 and above modes you
use 80 conductor cables.
Please assure that ribbon cables are no longer than 45cm.
In case of rounded ATA cables, the length depends on the
quality of the cables.
SATA cables can be up to 1m long according to the specification.
Static device numbering
(enabled with the
reserves a number for each possibly connected disk,
even when not present.
This is useful in hotswap scenarios
where disks should always show up as the same numbered device,
and not depend on attach order.
Native Command Queuing (NCQ) on SATA drives is not yet supported.