Date   : Fri, 14 Sep 2007 16:08:12 +0100
From   : francis@... (Francis Devereux)
Subject: Working out disk sizes...

On Fri, Sep 14, 2007 at 02:45:33PM +0100, Jules Richardson wrote:
> 
> [probably an obvious answer - I'm not next to a BBC with which to check]
> 
> Armed with a BBC that's both DFS and ADFS-capable, what's the most painless 
> way of working out the geometry of an unknown floppy:
> 
>    1) Filesystem type, side 0 (DFS, ADFS, unknown)
>    2) Track count, side 0 (40 or 80)
>    3) Filesystem type, side 1 (DFS, ADFS, unknown)
>    4) Track count, side 1 (40 or 80)
> 
> ... just trying to bring up a catalogue using the appropriate ROM (DFS or 
> ADFS) seems like a good start, 

Yes, although it can take a while for ADFS to give an error message if you
try to catalogue a DFS disk (I can't remember how long the other way round
takes).

> however I'm not sure if it's obvious from the 
> catalogue data whether a disk (DFS or ADFS) was formatted 40 or 80 track?
> 
> Furthermore, doesn't ADFS have the option of spanning both disk surfaces - is 
> it obvious from the side 0 catalogue of such a disk that the second surface is 
> an extension of the first?

There are only 3 types of ADFS floppy:
Small  - 160K single sided 40 track
Medium - 320K single sided 80 track
Large  - 640K double sided 80 track

so *FREE is enough to tell the difference.

Not sure about DFS floppies; I haven't used any of the double-density DFSes
much so I'm not sure what DFS formats are available.

Francis

> 
> (JOOI, what was the definitive ADFS reference for the 8-bit machines? Whilst 
> DFS seems to have been covered in specific books from both Acorn and others, I 
> don't think I've ever come across any equivalent for ADFS)
> 
> cheers
> 
> Jules
> 
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