NAME    [Toc]    [Back]

     atapiscsi - ATAPI<->SCSI adapter

SYNOPSIS    [Toc]    [Back]

     atapiscsi* at wdc? channel ? flags 0x0000
     atapiscsi* at pciide? channel ? flags 0x0000
     scsibus* at atapiscsi?

DESCRIPTION    [Toc]    [Back]

     The atapiscsi driver supports ATAPI (also  called  IDE)  devices such as CDROMs,
  ZIP  drives,  LS-120  floppy drives, and tape drives.
All ATAPI devices
 talk a subset of the SCSI protocol.

     The atapiscsi driver acts like a SCSI  adapter.   Thus,  the
ATAPI devices
     connected  to the system will appear as SCSI devices.  ATAPI
CD-ROMs will
     appear as cd(4) devices, ATAPI tape drives as st(4) devices,
and ATAPI
     floppies as sd(4) devices.

     For  performance  reasons, one should avoid putting an ATAPI
device and a
     hard disk on the same cable.  The driver  does  not  support
bus release
     and,  even  if it did, many ATAPI devices do not support it.
There is only
     one command outstanding on a cable at a time.  For  example,
if a hard
     disk  and  a CD drive are placed on the same cable, the hard
disk requests
     may get queued behind slower CD operations.

     The flags are used only with controllers  that  support  DMA
operations and
     mode settings (like some pciide(4) controllers).  The lowest
order
     (rightmost) nibble of the flags define the PIO mode to  use.
The next
     four bits indicate the DMA mode and the third nibble 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
     UltraDMA, 0xf (1111)  means  ``disable''.   For  example,  a
flags value of
     0x0fac  (1111 1010 1100) means ``use PIO mode 4, DMA mode 2,
disable
     UltraDMA''.  The special setting 0x0000 means ``use whatever
the drive
     claims to support''.

SEE ALSO    [Toc]    [Back]

     cd(4), intro(4), pciide(4), scsi(4), sd(4), st(4), wdc(4)

BUGS    [Toc]    [Back]

     Slow  devices,  like  tape  drives, could do a better job of
sharing the
     channel.  For now, we recommend you put the tape  device  on
its own channel.


OpenBSD      3.6                           July      25,     1999