.\"	$OpenBSD: fdc.4,v 1.9 2004/03/21 19:50:44 miod Exp $
.\"	$NetBSD: fdc.4,v 1.6 1996/03/22 01:55:14 andrew Exp $
.\"
.\" Copyright (c) 1996 Andrew C. Wheadon
.\" Copyright (c) 1983, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\"     @(#)fdc.4	8.1 (Berkeley) 3/22/96
.\"
.Dd March 25, 1996
.Dt FDC 4
.Os
.Sh NAME
.Nm fdc
.Nd NEC765 compatible floppy disk driver
.Sh SYNOPSIS
.Cd "fdc0 at isa? port 0x3f0 irq 6 drq 2"
.Cd "fd* at fdc? drive ? flags 0x00"
.Sh DESCRIPTION
The
.Nm
driver supports the standard AT floppy disk controllers.
These include standard IDE, MFM, RLL,
EIDE, ESDI, and SCSI controllers with floppy attachment.
.Pp
The standard names of a floppy drive will take the form
.Pa /dev/fd{0,1,2,3}{,B,C,D,E,F,G,H}[a-p] .
.Pp
The first component of this path is the unit number, permitting
a total of 4 floppy drives.
The next component is missing for the default geometry (it
would be A, but it is omitted for simplicity) and B-H for the
other 7 geometry types the floppy driver supports.
The last component of the path is the 16 partitions that a floppy
disk can support.
.Pp
The additional geometry types are as follows:
.Pp
.Bl -tag -width xxxxxx -offset indent -compact
.It `B' 1.44MB
.It `C' 1.2MB
.It `D' 360KB/AT (360KB disk in a 1.2 MB drive)
.It `E' 360KB/PC (360KB drive)
.It `F' 720KB
.It `G' 720KB/x (720KB in a 1.2 MB drive)
.It `H' 360KB/x (360KB in a 720KB drive)
.El
.Pp
The default geometry is the format specified in the BIOS, and
is typically the largest supported format.
.Pp
Some floppy controllers do not respond correctly to probes, and
the configuration file
.Cm flags
field can be used to specify a particular drive type, overriding the
probed type.
If the 0x10 bit is on, the low order three bits of the
.Cm flags
field encode the drive type, as follows:
.Pp
.Bl -tag -width 2.88MB -offset indent -compact
.It 1 2.88MB
.It 2 1.44MB
.It 3 1.2MB
.It 4 720K
.It 5 360K
.It 6 1.2 MB Japanese format
.El
.Pp
If the 0x20 bit is on, the drive will be attached even
if it was not found by the probe routine.
.Sh SEE ALSO
.Xr intro 4 ,
.Xr isa 4
.Sh BUGS
The
.Nm
driver can interfere with other controllers, namely some WD/SMC
network controllers fail to work when the probing mechanism
in the
.Nm
driver probes for a missing second floppy drive.
In this case you should try recompiling the kernel
replacing the relevant line with
.Cd "fd0 at fdc? drive ?" .