[comp.os.minix] Multiformat floppies Was: ST Minix 1.5 floppy driver and serial driver questions

klamer@mi.eltn.utwente.nl (Klamer Schutte -- Universiteit Twente) (01/08/91)

ta_cook@eisvxe.moundst.mn.org (Thomas A. Cook) writes:

>Awhile back I remember some discussion about Minix for the ST being able to read
>the disk label to determine the size of the disk and the ablility to read 800Kb
>formatted (vs the 720Kb standard formatted) disks.

>Am I remembering this correctly or not.  If there is such a patch available
>where can I find it (non-FTP)?

There is such a patch for minix 1.1. But this one does not patch cleanly
to 1.5.

But there is a problem with this approach. You are creating a device which
can be resized according to the data you write to it.
(Suppose you have a 820k floppy. You write a tar file to the device /dev/dd0.
 Now you have a tar file at the 82/10/2 style floppy. But...
 Next time you open the device, its bootblock( phys. block 0 ) will be
 corrupted (i.e. it will be the tar file header). So you can't read your 
 information anymore)

The correct way (IMHO):
Make several minor devices point to several physical layouts. This will
ensure that the problem above will not occur.
Disadvantage: You have to remember what way the floppy is initialized.
 But you had to do that anyway (problem of double/single sided floppies).

Having this implemented i now can read my 82/10/2 floppies on minix 1.5.10
But not tested to good (i have a hard disk now :-))

When there are request, i can post the diffs.

Greetings, Klamer

PS with a 82/10/2 floppy i mean 82 tracks, 10 sectors and 2 sides.
   I think this is the biggest safe size on a standard ST.

-- 
Klamer Schutte
Faculty of electrical engineering -- University of Twente, The Netherlands
klamer@mi.eltn.utwente.nl	{backbone}!mcsun!utrcu1!utep!utelmi01!klamer