Manual Pages  — FDCONTROL

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.amp; /dev/fd0.

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.

$ fdcontrol /dev/fd0
1.44M

$ fdcontrol -v /dev/fd0
/dev/fd0: 1.44M drive (3.5" high-density)

$ fdcontrol -F /dev/fd0
18,512,0xff,0x1b,80,500,2,0x6c,1,0,+mfm

/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>

# fdcontrol -s 16,128,0x80,0x2,40,300,,0x10,,,-mfm,+2step /dev/fd1.1

fdcontrol -s  26,128,0x80,0x2,77,500,2,0x10,,,-mfm /dev/fd0

fdc(4)