.\"
.\" Copyright (c) 1994 Wilko Bulte
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
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.\" 3. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" $FreeBSD: src/share/man/man4/fdc.4,v 1.20.2.5 2001/10/01 13:07:23 dd Exp $
.\" $DragonFly: src/share/man/man4/fdc.4,v 1.2 2003/06/17 04:36:59 dillon Exp $
.\"
.Dd August 31, 1994
.Dt FDC 4
.Os
.Sh NAME
.Nm fdc
.Nd PC architecture floppy disk controller driver
.Sh SYNOPSIS
.Cd "device fdc0 at isa? port IO_FD1 flags 0x1 irq 6 drq 2"
.Cd device fd0 at fdc0 drive 0
.Cd device fd1 at fdc0 drive 1
.Sh DESCRIPTION
This driver provides access to floppy disk drives and QIC40/80 tapedrives.
In /dev for each floppy device a number of minor devices are present.
The
/dev/fd* devices with trailing alphabetic characters are used to indicate
.Sq partitions
on the floppy disk.
The /dev/fd*.<number> are devices that
indicate the size of the floppy disk (so: 720kB, 1440kB etc). The latter
are used for formatting disks using fdformat or for accessing different
density disks in multidensity drive.
Example: 720kB disk in a 1.44Mb drive.
.Pp
Normally, the driver will ask the system's CMOS memory to obtain the
floppy drive configuration.  Some machines do not store any form of a
configuration value in their CMOS.  Use the flags value
.Ql 0x1
to pretend a 1.44 MB floppy drive as the first unit, without asking the
CMOS for it.
.Pp
The flags value
.Ql 0x2
is reserved for PCMCIA floppy use, and should never be set in a
configuration file directly.  It is internally handled in the driver
if the compilation option
.Dv FDC_YE
is set, and defers device probing.
.Pp
Normally, the device driver detects FDC chipsets that have an internal
FIFO, and enables the FIFO on them.  There is a slight chance that this
feature is actually misdetected (seen on an IBM Thinkpad 755c), so it
can be turned off using flags
.Ql 0x4 .
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /dev/fd*
floppy disk device nodes
.It Pa /dev/fd*. Ns Ar "<size in kB>"
floppy disk device nodes where the trailing number indicates the floppy
capacity
.It Pa /sys/i386/conf/GENERIC
sample generic kernel config file
.It Pa /sys/isa/fd.c
floppy driver source
.El
.Sh SEE ALSO
.Xr fdformat 1 ,
.Xr disktab 5