FDCONTROL(8) FreeBSD System Manager's Manual FDCONTROL(8)
NAME
fdcontrol - display and modify floppy disk parameters
SYNOPSIS
fdcontrol [-F] [-d dbg] [-f fmt] [-s fmtstr] [-v] device
DESCRIPTION
The fdcontrol utility allows the modification of the run-time behavior of
the fdc(4) driver for the device specified by device.
Commands are implemented to query the current device density settings as
well as the underlying device hardware as registered with the driver, to
manipulate debugging levels, and to adjust the device density settings.
All the operations that manipulate the kernel settings are restricted to
the superuser (by the device driver), while all inquiry requests only
require read access to device.
The device argument should always be given as a full path name, e.g.
/dev/fd0.
Inquiry Commands
Running the fdcontrol utility without any of the optional flags will
report the drive type that is registered with the device driver. In the
shortest form, a single string describing the drive type will be
returned. Possible values are: "360K", "1.2M", "720K", "1.44M", "2.88M",
or "unknown". This information is primarily intended to be easily
parsable by scripts.
In order to add some descriptive text that makes the output better human
readable, the flag -v can be added.
Specifying flag -F will report the device's density settings in a form
that is suitable as input to the -s fmtstr option (see below). Again,
together with -v, some more text will be returned, including the total
capacity of the density settings in kilobytes.
Debug Control
The fdc(4) control utilities support two different options how to specify
device density settings. The first form uses -f fmt to specify the
format of the medium in kilobytes. Depending on the underlying drive
type, the value is compared against a table of known commonly used device
density settings for that drive, and if a match is found, those settings
will be used. Currently, the following values for the respective drive
types are acceptable:
2.88M and 1.44M drives:
KB sectrac secsize ncyls speed heads flags
1721 21 2 (512) 82 500 2 MFM
1476 18 2 (512) 82 500 2 MFM
1440 18 2 (512) 80 500 2 MFM
1200 15 2 (512) 80 500 2 MFM
820 10 2 (512) 82 250 2 MFM
800 10 2 (512) 80 250 2 MFM
720 9 2 (512) 80 250 2 MFM
1.2M drives:
KB sectrac secsize ncyls speed heads flags
1200 15 2 (512) 80 500 2 MFM
1232 8 3 (1024) 77 500 2 MFM
1476 18 2 (512) 82 500 2 MFM
1440 18 2 (512) 80 500 2 MFM
1200 15 2 (512) 80 500 2 MFM
820 10 2 (512) 82 300 2 MFM
800 10 2 (512) 80 300 2 MFM
720 9 2 (512) 80 300 2 MFM
360 9 2 (512) 40 300 2 MFM,2STEP
640 8 2 (512) 80 300 2 MFM
720K drives:
KB sectrac secsize ncyls speed heads flags
720 9 2 (512) 80 250 2 MFM
360K drives:
KB sectrac secsize ncyls speed heads flags
360 9 2 (512) 40 250 2 MFM
The second form to specify a device density uses -s fmtstr to explicitly
specify each parameter in detail. The argument fmtstr is a comma-
separated list of values of the form:
sectrac,secsize,datalen,gap,ncyls,speed,heads,f_gap,f_inter,offs2,flags
The meaning of the parameters is:
sectrac The number of sectors per track.
secsize The sector size code, 0 = 128 bytes (or less), 1 = 256
bytes, 2 = 512 bytes, 3 = 1024 bytes.
datalen The actual sector size if the size code is 0, or the
(ignored) value 0xFF for larger size codes.
gap The length of the gap 3 parameter for read/write operations.
ncyls The number of cylinders.
speed The transfer speed in kilobytes per second. Can be 250,
300, 500, or 1000, but each drive type only supports a
subset of these values.
heads The number of heads.
f_gap The length of the gap 3 when formatting media.
f_inter The sector interleave to be applied when formatting. 0
means no interleave, 1 means 1:1 etc.
offs2 The offset of the sector numbers on side 2 (i.e., head
number 1). Normally, sector numbering on both sides starts
with 1.
flags A list from one of the following flag values:
+mfm Use MFM encoding.
-mfm Use FM (single-density) encoding.
+2step Use 2 steps per each cylinder (for accessing
40-cylinder media in 80-cylinder drives).
-2step Do not use 2 steps per cylinder, i.e., access
each physical cylinder of the drive.
+perpend Use perpendicular recording (for 2.88 MB
media, currently not supported).
-perpend Use longitudinal recording.
For any missing parameter, the current value will be used, so only actual
changes need to be specified. Thus to turn off a flag bit (like +mfm
which is the default for all drive types), the form with a leading minus
sign must explicitly be used.
EXAMPLES
A simple inquiry about the drive type:
$ fdcontrol /dev/fd0
1.44M
Same as above, but with verbose output. Note that the result is about
the drive type, as opposed to a device density, so it is independent from
the actual subdevice being used for device.
$ fdcontrol -v /dev/fd0
/dev/fd0: 1.44M drive (3.5" high-density)
Inquiry about the density settings:
$ fdcontrol -F /dev/fd0
18,512,0xff,0x1b,80,500,2,0x6c,1,0,+mfm
The verbose flag makes this human readable:
/dev/fd0: 1440 KB media type
Format: 18,512,0xff,0x1b,80,500,2,0x6c,1,0,+mfm
Sector size: 512
Sectors/track: 18
Heads/cylinder: 2
Cylinders/disk: 80
Transfer rate: 500 kbps
Sector gap: 27
Format gap: 108
Interleave: 1
Side offset: 0
Flags <MFM>
As indicated, trailing commas in the parameter list may be omitted.
In order to access archaic 160 KB single-density (FM encoded) 5.25 media
in a modern 1.2M drive, something like the following definition would be
needed. (Note that not all controller hardware is actually capable of
handling FM encoding at all.)
# fdcontrol -s 16,128,0x80,0x2,40,300,,0x10,,,-mfm,+2step /dev/fd1.1
It is still possible to hook up 8" drives to most modern floppy
controllers, given the right cable magic. (On PC hardware, tell the BIOS
that it is a 5.25" drive.) The classical 128/26/2/77 format can be read
with this entry
fdcontrol -s 26,128,0x80,0x2,77,500,2,0x10,,,-mfm /dev/fd0
SEE ALSO
fdc(4)
HISTORY
The fdcontrol utility appeared in FreeBSD 2.0, and was vastly overhauled
in FreeBSD 5.0.
AUTHORS
The program and this man page was contributed by J"rg Wunsch, Dresden.
FreeBSD 13.1-RELEASE-p6 April 7, 2017 FreeBSD 13.1-RELEASE-p6
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