Date   : Sat, 18 Feb 2006 23:16:53 +0000
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: Watford / Acorn DFS question

Jules Richardson <julesrichardsonuk@...> wrote:
> > Unless I've misunderstood your question, Watford disks have two
> > catalogues if formatted with 62 files - otherwise they look just like
> > Acorn discs.
> 
> Ahhh, OK - so:
> 
> If it's got a second catalogue it's a Watford disk and also supports longer
> files (by optionally setting the high bit in byte 5 of the filename).
 
No. If it's got a second catalogue, it's a Watford 62-file disk.
Full stop. Nothing else. Absolutely *NOTHING* implied about the
support or otherwise of longer files.
 
*IF* byte &106 b3-b2 are %01, *THEN* it's a Watford disk that
supports longer files by setting b7 in byte 5 of the filename.
Full stop. Nothing else. Absolutely *NOTHING* implied about the
presence or otherwise of a second catalogue.
 
> If there's no second catalogue, it's just a standard Acorn-compatible DFS
> disk, with no longer file support.
 
*IF* byte &106 b3-b2 are %00, *THEN* it's a standard Acorn-
compatible disk with no longer file support. Full stop. Nothing
else. Absolutely *NOTHING* implied about the presence or otherwise
of a second catalogue.
 
> (I'm primarily using JGH's DFS format page - which suggests that the second
> catalogue is optional on Watford disks. If it's mandatory then that means I
> *can* differentiate between a Watford and Acorn disk, making life a bit
> easier! :-)
 
You *CANNOT* differentiate between a 31-file Watford disk smaller
then 256K and a standard Acorn DFS disk. That's the whole point.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
BBC IDE Hard Drive Interface - http://mdfs.net/Info/Comp/BBC/IDE