@node Interesting formats, Command Index, Acronyms, Top
@appendix Interesting formats

This table lists a few interesting formats.  Some of them are not
included in the table of predefined formats due to lack of space.  You
may use these by setting the geometry of the variable geometry device
using @code{setfdprm}.  Most of the entries in the following table do
not describe a single format, but rather a family of formats which share
a common characteristic.  For this reason, no precise parameters are
included.

@table @strong

@item 80/90/160/180 KB 5.25"
Original IBM PC, CP/M, Apple II, TRS-80, etc.  Single density, FM
(not MFM), 40-track.  Some systems also used "hard" sectoring, with
an index hole for each sector.  These are probably readable on
standard FDCs if anyone cares to go to the effort.  160KB/180KB
formats were double-sided.

@item 320 KB 5.25"
CP/M, Zenith Z-100, some forms of MS-DOS.  8-sector DD 40-track.

@item 400 KB 5.25"
AT&T 7300/3B1: cpio format, 10 sectors, DS, 40 tracks.

PC: MS-DOS, 10 sectors, DS, 40 tracks; formatted by various
utilities; readable by some versions of MS-DOS.

@item <720KB 3.5" formats

@itemize @bullet
@item
Some dedicated word-processing systems use lower than normal capacity
floppies (some may be 40-track either via "stretching" or by having odd
drives; others may be single-sided or use fewer sectors per track, or
use "single density" or FM).

@item
Atari ST 360 KB floppies: these are 9 sector 250kb/s 80-track
single-sided, using a slightly incompatible MS-DOS-like FAT.  Very
common distribution format for Atari ST software.

@item
Mac 400 KB: single-sided 80-tracks, Mac MFS or HFS file system, Group
Code Recording, zone bit recording, variable RPMs from 300 to 600 in 5
zones, and auto-eject mechanism.  Impossible to read on normal PC drives
without some form of hardware assistance.
@end itemize

@item 720 KB 3.5"
@itemize @bullet
@item
PC: 9 sectors, DS, 80-track; very common.
@item
Atari ST: same as Atari ST 360 KB except double-sided.
@end itemize

@item 720 KB 5.25"
"Quad Density": 9 sectors, DS, 80-track; name is rather misleading,
as it is double density 80 track.

@item 800 KB
@itemize @bullet
@item
PC: 10 sectors, DS, 80 tracks; readable by MS-DOS; formatted by
many PC utilities; "almost standard".
@item
Atari ST "Twister": 10 sectors, DS, 80-track; slightly incompatible
MS-DOS-like FAT; sector skewing (originated by David Small).
@item
Mac 800 KB: same as Mac 400KB except double-sided.
@end itemize
@item 880 KB

@itemize @bullet
@item 
PC: 11 sectors, DS, 80 tracks, interleaved(?).  Formatted by various PD
utilities such as fdformat.
@item
Amiga: uses "single-sector" tracks the size of 11 sectors; DS; 80
tracks.  Written by a custom chip rather than a standard FDC; it is very
difficult to access these using a standard FDC, though it might be
possible in theory, using some trickery.
@end itemize

@item 880 KB - 960 KB
Atari ST: 11/12 sectors, DS, 80-track, interleaved(?); not very
reliable, formatted by various PD utilities.

@item 960 KB
2m and Linux; 6 sectors interleaved(?), DS, 250kb/s?, 80-track, 1K
sectors(?).

@item 1001 KB
"Japanese" format: 300kb/s, 77 tracks, HD drives/disks.

@item 1040 KB
2m and Linux only; 13 sectors, DS, 300kb/s, 80-track.

@item 1120 KB
2m and Linux only; 14 sectors interleaved, DS, 300kb/s, 80-track.  Can
only be formatted on Linux; even on Linux, it is difficult to format
these on an ED drive.

@item 1200 KB 5.25" HD
"AT": 360 rpm 500kb/s 80-track 15-sector MS-DOS.

@item 1360 KB 5.25" HD
Highest "fdformat" noninterleaved 5.25" format.  360 rpm 500kb/s
17-sector MS-DOS.

@item 1440 KB 5.25" HD
Interleaved 18-sector 360 rpm 500kb/s; highest "fdformat" 5.25" format.
18-sector MS-DOS.

2m and Linux only: noninterleaved 1024-byte sector 18-sector-equivalent
360 rpm 500kb/s; 18-sector MS-DOS.  A good substitute for 1.44MB 3.5"
floppies.

@item 1600 KB 5.25" HD
2m and Linux only: interleaved?  500kb/s 80-track; 1 8KB sector, 1
2KB sector?

@item 1760 KB 3.5" HD
2m and Linux only: 11 1KB sectors; 500kb/s, noninterleaved?

@item 1840 KB 3.5" HD
2m and Linux only: 23-sector equivalent; 500kb/s, noninterleaved.

@item 1920 KB 3.5" HD
2m and Linux only: 3 4KB sectors; 500kb/s, interleaved?

2m and Linux only: 1 8KB sector, 1 4KB sector; 500kb/s, interleaved?

@item 2880 KB 3.5" ED
"Extra Density" or "Extra High Density".   1 Mb/s, 36-sector, DS, 80-
track.

@item 3200 KB 3.5" ED
Non-interleaved, 80 track, 40-sector 1 Mb/s.  Highest capacity that
MS-DOS can read directly(?)

@item 3520 KB 3.5" ED
2m and Linux only: 1 16KB sector, 1 4KB sector, 1 2KB sector?
Non-interleaved, 80 track 1 Mb/s.  Highest capacity that 2m can format.

@item 3840 KB 3.5" ED
2m and Linux only: 1 16KB sector, 1 8KB sector (or is it 3 8KB
sectors?).  Non-interleaved, 80 track 1 Mb/s.  Formatted only by Linux,
but readable and writeable by 2m.
@end table


Linux is able to read almost any MFM disk. These include many CP/M disks
and also Commodore 1581 disks. Please get Michael Haardt's documentation
on floppy drives for a detailed description of those formats. This can
be ftp'ed from the following location:
@example
ftp://cantor.informatik.rwth-aachen.de/pub/linux/floppy.ps
@end example

Commodore 1581 disks are not yet described in this documentation.  Use
@code{setfdprm /dev/fd0 DD DS sect=10 cyl=80 swapsides}. If you want to
use these disks often, redefine one of the "default" formats to be
Commodore 1581, and then put it into the autodetection list for the
drive. The following example describes how to redefine format number 31
(minor device number 124) to be Commodore 1581:
@example
mknod /dev/fd0cbm1581 b 2 124
setfdprm /dev/fd0cbm1581 DD DS sect=10 cyl=80 swapsides
floppycontrol --autodetect /dev/fd0 31,7,8,4,25,28,22,21
@end example

The two latter commands have to be issued after each reboot, so I
suggest you put them into your @file{/etc/rc} files if you use many
Commodore 1581 disks.
