ATAPISCSI(4)              OpenBSD Programmer's Manual             ATAPISCSI(4)

NAME
     atapiscsi - ATAPI<->SCSI adapter

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

DESCRIPTION
     The atapiscsi driver supports ATAPI (also called IDE) devices such as CD-
     ROMs, ZIP drives, LS-120 floppy drives, and tape drives.  All ATAPI de-
     vices 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
     cd(4), intro(4), pciide(4), scsi(4), sd(4), st(4), wdc(4)

BUGS
     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 chan-
     nel.

OpenBSD 4.7                      May 31, 2007                                1
