The extended floppy densities are called xd
(extended double) and
xh
(extended high). They fit more data on a floppy by going outside
the `factory specifications' of the floppies and drives. For example,
on 3.5" DD floppies, the normal d
(double) density format uses 80
tracks and 9 sectors per track, the xd
format uses 82 tracks and 10
sectors per track, which fits 820 Kb. on the floppy.
Tbackup needs the setfdprm
program to use extended densities. I
have no idea when this program first appeared in Linux, so you may
not have it.
Not all floppies and/or floppy drives are able to go outside their
`factory specifications' and hold extra data. For example, my 5.25"
drive can't read and write xd
density. Most modern 3.5" HD drives
however have no problems reading and writing extended densities.
To find out which extended densities your drives support, just experiment with tbackup and trestore.
Due to limitations in the Linux kernel, reading and writing 1.7 Mb. on
3.5" HD floppies is extremely slow (some 8 times slower as normal
floppy access) xd
density for 3.5" floppies
virtually useless. There seems to be some non trivial patch needed to
the Linux kernel to allow fast writing of the 3.5" xd format.
Currently you can not use the xd
density if you have a DD floppy
drive, you can only use xd
and xh
on a HD drive. I haven't found
the xd
formatting parameters needed for DD drives, if you have them
please let me know.
If you are actually going to make backups with extended densities,
make sure that you have access to at least one other machine that
supports them. This other computer need not be a Linux machine, there
are also MS-DOS packages that support extended densities. I have one
called fdformat
, archive name FDFORM17.ZIP
.
If you want to read or write extended density floppies under Linux outside tbackup, you will have to edit some configuration files first.
/etc/fdprm
:
#Extended densities used by tbackup (5.25 xd and xh, 3.5 xd and xh)
410/1200 820 10 2 41 1 0x25 0x02 0xDF 0x2E
1476/1200 2952 18 2 82 0 0x25 0x00 0xDF 0x02
820/1440 1640 10 2 82 0 0x25 0x01 0xDF 0x2E
1722/1440 3444 21 2 82 0 0x25 0x00 0xDF 0x0C
/etc/mtools
file contains the lines
A /dev/fd0 12 0 0 0
B /dev/fd1 12 0 0 0
for the a
: and b
: drives.Before accessing an extended density floppy, type the command
setfdprm -p /dev/fdnr name
where nr is the floppy drive number, 0 or 1, and name is
410/1200
for the xd
format in a 5.25" drive1476/1200
for the xh
format in a 5.25" drive820/1440
for the xd
format in a 3.5" drive1722/1440
for the xh
format in a 3.5" drivemdir a:
or mdir b:
and other mtools
commands to access the floppy.
You can also mount it with
mount -t msdos /dev/fdnr mountpoint
Formatting is possible with
fdformat -n /dev/fdnr
where the -n
option switches off the verify pass as verification of
extended floppy formats won't work with the current version of fdformat.
You can do a simple verify by hand by typing
cp /dev/fdnr /dev/null
and looking if cp
gives an error.
If you are finished with the floppy, you sometimes may have to type
setfdprm -c /dev/fdnr
to get the drive back in `autodetect mode' so that it will accept
normal floppies again.
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