.\"	$OpenBSD: atapiscsi.4,v 1.9 2003/06/06 10:29:41 jmc Exp $
.\"
.\" Copyright (c) 1999 Constantine Sapuntzakis.
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.Dd July 25, 1999
.Dt ATAPISCSI 4
.Os
.Sh NAME
.Nm atapiscsi
.Nd ATAPI<->SCSI adapter
.Sh SYNOPSIS
.Cd "atapiscsi* at wdc? channel ? flags 0x0000"
.Cd "atapiscsi* at pciide? channel ? flags 0x0000"
.Cd "scsibus* at atapiscsi?"
.Sh DESCRIPTION
The
.Nm
driver supports ATAPI (also called IDE) devices such as CD-ROMs, ZIP
drives, LS-120 floppy drives, and tape drives.
All ATAPI devices talk a subset of the SCSI protocol.
.Pp
The
.Nm
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
.Xr cd 4
devices, ATAPI tape drives as
.Xr st 4
devices, and ATAPI floppies as
.Xr sd 4
devices.
.Pp
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.
.Pp
The
.Cm flags
are used only with controllers that support DMA operations and
mode settings (like some
.Xr pciide 4
controllers).
The lowest order (rightmost) nibble of the
.Cm flags
define the PIO mode to use.
The next four bits indicate the DMA mode and the third nibble the UltraDMA
mode.
.Pp
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
.Dq disable .
For example, a
.Cm flags
value of 0x0fac (1111 1010 1100)
means
.Do
use PIO mode 4, DMA mode 2, disable UltraDMA
.Dc .
The special setting 0x0000 means
.Dq use whatever the drive claims to support .
.Sh SEE ALSO
.Xr cd 4 ,
.Xr intro 4 ,
.Xr pciide 4 ,
.Xr scsi 4 ,
.Xr sd 4 ,
.Xr st 4 ,
.Xr wdc 4
.Sh 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 channel.