[BBC-Micro] Disc formats -- DFS/ADFS and the Master Welcome Disc

Jonathan Graham Harston jgh at arcade.demon.co.uk
Thu Jan 21 22:39:41 GMT 2010


Message-ID: <4B57B53A.6000704 at philpem.me.uk>
 
Philip Pemberton wrote:
> Does anyone know if t00h0 is formatted differently on the Master welcome
> disc?
 
Track 0 is in the same physical place whether the drive is set to
step 80 tracks or 40 tracks. It is formatted as a usual DFS track 0
with the usual first 10 DFS sectors in it. 
 
> I'm also interested in any information folks might have on the DFS and
> ADFS formats (especially the 800K and 1.6MB ADFS "E" formats used on the
> Acorn Archimedes/RiscPC systems). I noticed JGH has some info on DFS and
> the earlier versions of ADFS, but ADFS-E info seems to be a bit thin on
> the ground.... :-/
 
RISC OS PRMs p2-195 onwards. I'll type something up sometime.
Essentially all ADFSs - prior to long-filename ADFSs - are the
same, the physical layout of the disk is different.
 
ADFS-L 16 sectors of  256 bytes, old map, 47-entry directories
ADFS-D  5 sectors of 1024 bytes, old map, 77-entry directories
ADFS-E  5 sectors of 1024 bytes, new map, 77-entry directories
ADFS-F 10 sectors of 1024 bytes, new map, 77-entry directories
 
ADFS-L is sequential (all up one side, then all up the other),
other ADFSs are interleaved (top, bottom, top, bottom, etc.)
 
-- 
J.G.Harston - jgh at arcade.demon.co.uk - mdfs.net/User/JGH
Whitby Yards Gazetteer - http://mdfs.net/Docs/Books/YofWhitby/Gazetteer



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