Date   : Fri, 21 Jun 1996 21:56:22 +0100
From   : Mike Tomlinson <mike@...>
Subject: Re: *INFO output required

In message <199606201159.NAA23052@...>, Mark de Weger
<deweger@...> writes
>
>
>Incidentally, does anybody know which non-standard DFSs are
>still in use by more than, say, 10 persons?
>
:)  Weren't there a couple hundred "non-standard" DFSes?

Most third party DFSs made a fairly good crack at being compatible with
the Acorn DFS. In particular, the Watford ones were particularly good,
adding many extra features over and above the Acorn version without
sacrificing too much compatibility. The Watford 1.43 release had nice
informative error messages which were truncated in the 1.44 release to
make room for the Tube host code.

I would suggest that compatibility between different DFSs comes down to
whether they supported the 8271 or 1770 controller. The addition of
double density in the 1770 meant that DFSs written for it necessarily
functioned somewhat differently to the 8271 versions. That said, the
Acorn 1770 DFS (v2.23) was very similar in operation to 8271 DFS v0.90
and 1.20: the same can be said for the later Watford DFSs. It got to the
point that despite the disk controller being radically different, the
DFS was able to load disks with software protection without too much
trouble. ISTR that the Acorn 1770 allowed you to hold down different
keys at bootup to allow selection of different attempts at 8271
emulation for loading protected software.

The auto 40/80 and auto single/double density detection in the Watford
1.44 DFS/DDFS were great features.

IMHO, the worst DFSs were the Solidisk and Opus double density ones.
These allowed for a more flexible FAT and directory structure of the
disk but at the cost of compatibility.

I have a truckload of BBC disks of software which I would be glad to
upload to a website: any takers? A disk reader to allow me to read the
disks directly in my 1.2 drive would be a boon, but I understand from
Wouter S.'s home page that some el cheapo PC floppy controller cards
have a broken single density emulation. I have downloaded the BBC disk
reader and will try it out this weekend.

-- 
Mike Tomlinson
constructive email to mike@...               ; flames to /dev/null.