Date   : Thu, 22 Dec 2011 13:18:45 +0000
From   : dl.harper@... (David Harper)
Subject: ADFS directories - "reserved" bytes

On 22/12/11 12:09, Andrew Benham wrote
> ...
>
> I ought to check my (5.25") DOS Plus floppies, because this was (I
> believe) the first outing of Acorn's 800kB disk format - although only
> the first floppy is ADFS (and only the first part of that disk too).
>
> ...
The first of the DOS Plus floppies is 640kB mixed ADFS/DOS - in fact 
only one track of one side is ADFS (and it doesn't need all of that - 3 
sectors are filled with rubbish); the rest of the disk is DOS, though 
with 256-byte sectors and in ADFS order (all of side 0 then all of side 1).

The remaining 3 of the DOS Plus floppies are 800kB DOS - 1024-byte 
sectors, 5 sectors per track, but with no boot sector and with a single FAT.

David Harper