ND floppy disks

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Norsk Data floppy disks were originally only 8", but this later changed to 5 1/4". Newer systems would come with a dual 8" and 5 1/4" unit, and all ND software (e.g. SINTRAN-III and patch updates) were delivered on 5 1/4" floppies after the introduction of the smaller drives.

Both the 8" and in particular the 5 1/4" controllers could support a number of formats.

Formats supported by the 3027 floppy controller, 3106 and 3112 floppy/streamer controllers:

(The old PIO floppy disk controller supports only formats 0b, 1b, 2b)

Format Identification Sector size Sectors/t Tracks/s Sides/Density Capacity pages
0b IBM SYS-32-II 512 bytes/sector 8 77 SS/SD 154
1b IBM 3600 256 bytes/sector 15 77 SS/SD 144
2b IBM 3740[1] 128 bytes/sector 26 77 SS/SD 125
3b -
4b Non IBM 512 bytes/sector 8 77 DS/SD 308
5b Non IBM 256 bytes/sector 15 77 DS/SD 288
6b Non IBM 128 bytes/sector 26 77 DS/SD 250
7b -
10b Non IBM 512 bytes/sector 15 77 SS/DD 288
11b IBM SYS-34 256 bytes/sector 26 77 SS/DD 250
12b -
13b Non IBM 1024 bytes/sector 8 77 SS/DD 308
14b Non IBM 512 bytes/sector 15 77 (80*) DS/DD 577
15b IBM SYS-34 256 bytes/sector 26 77 DS/DD 500
16b -
17b Non IBM 1024 bytes/sector 8 77 DS/DD 616

[*]Format 14b allows usage of tracks 78-80 as well, but these tracks must be formatted with the format track function.

Additional formats only handled by the 3112 card:

Format Identification Sector size Sectors/t Tracks/s Sides/Density Capacity pages
20b -
21b -
22b Basic 5 1/4" 128 bytes/sector SS/SD
23b - 33b -
34b IBM PC[2] 512 bytes/sector 15 80 DS/DD 600
35b - 57b -
60b - 77b User specified

Format identification numbers

The format identification number in the left column of the table was used to switch the floppy disk controller to the desired format before use, e.g. via the Sintran command DEVICE-FUNCTION.

Standard Norsk Data formats

The standard Norsk Data formats floppies were format 0b for 8" floppies and format 17b for 5 1/4" floppies. Only formats 0b and 17b could be used for a Sintran III file system or as a sequential-media volume for the BACKUP-SYSTEM application[3]. The other formats could be used to support a foreign floppy disk format. Examples of the latter could be CP/M (8" single sided, single density, 128 bytes/sector, format 2b), or standard 80-track IBM PC 5 1/4" 1.25MB floppies (format 34b). None of the non-ND formats had built-in filesystem support in Sintran, so to read or write CP/M or IBM PC floppy disks the user would need to acquire or write specific software for it.

Details of the default 8" and 5 1/4" formats

8" format

The 8" Norsk Data format 0b was 512 bytes/sector, single sided/single density, 8 sectors per track, 77 tracks. The total capacity was 154 pages of 2048 bytes per page. Of this 148 pages could be allocated for files.

5 1/4" format

The 5 1/4" Norsk Data format 17b was 1024 bytes/sector, double sided/double density, 8 sectors per track, 77 tracks per side. The total capacity was 616 pages. Of this 612 pages could be allocated for files. Note that "double density" is actually so-called "1.2MB high density" format in PC terminology, sometimes called "DS/HD" or "MF2-HD". The 5 1/4" media is typically labelled "DS,HD 96TPI".

The floppy controller could use any of its supported formats on any media, 8" or 5 1/4", so it is also possible to have a format 17b 8" floppy disk. This became feasible when media with higher density became available.

ND sometimes transferred older 8" images to newer 5 1/4" floppy disks, without re-formatting the filesystem and format to format 17b. In this case the 5 1/4" floppy would use format 0b, which also implies FM (not MFM) encoding. This was not common, but these kind of floppies can (presumably) be identified via their PD sheets which will show 148 pages, or the floppy label which may have a label ID ending in -S (for 'single density). They may also have two dates, the older one will be the date of the original 8" image, and the newer will be the date of the transfer to 5 1/4" floppy.

Reading a Norsk Data floppy on a Linux computer

A Linux computer equipped with a 5 1/4" floppy disk controller can read a Norsk Data floppy of format 17b. To do this the setfdprm tool is needed, which can be found in either the fdutils package or the util-linux package, depending on distribution. The version should be 5.2 or newer.[4]

  • Insert the floppy disk
  • Close the lever arm
  • Enter the following command (as user root):
setfdprm /dev/fd0 sect=8 hd ssize=1024 cyl=77
  • The floppy can now be read with the following command:
dd if=/dev/fd0 bs=2048 count=616 of=file.image
  • Do not use the 'cat' command.
  • The setfdprm command must be repeated whenever a new floppy disk is inserted.
  • The floppy content will be found in the file.image file, or whatever output file defined by the of= parameter to the dd command.

If the above fails: Use this sequence instead of the single setfdprm command:

fdrawcmd recalibrate 0
setfdprm /dev/fd0 sect=8 hd ssize=1024 cyl=77

Do this for every new floppy. If you forget the 'setfdprm' the drive may get into a read-error cyclic problem. If so, then insert the following command (once) before continuing with fdrawcmd, setfdprm:

floppycontrol --resetnow 2

The above command, followed by the fdrawcmd recalibrate 0 command, will perform a full reset of the drive and 'setfdprm' should work afterwards. NB: Keep the floppy in the drive when executing these commands.

The format of the image data will normally be either a standard Sintran file system, or a backup volume. The Sintran file system is documented in Norsk Data Document ND–30.003 SINTRAN III System Supervisor .

References

  1. http://www.bitsavers.org/pdf/terak/terak.8510.description.pdf
  2. Wikipedia:IBM_Personal_Computer/AT
  3. Norsk Data Document ND–60.250 BACKUP USER GUIDE
  4. http://fdutils.linux.lu/disk-id.html