Date : Sun, 24 May 1998 17:32:49 +0100
From : jonripley@... (Jon Ripley)
Subject: Ideas on new hardware
Crispin Boylan <viewtronix@...> wrote:
>I can see a new DFS, ADFS and HDDFS (High Density DFS, nifty eh?) would
>need to be programmed.
IMHO Possibly more work than a lot of people would want to take up, even
with the knowlegde.
There were several double density DFS ROMs, some allowed 800k on a DFS disc
(more than the DOS 720k(!).
>Know any good 'DFSers'?
I have a disc that contains (AFAIK) full technichal information about DFS,
especially OSWORD &7F.
If you'd like a copy I should be able to send it to you.
>Another half-idea that I had would be to squeeze these three DFS's together
>onto one chip, each one sharing common code, whilst being individually
>selectable.
Solidisk had a similar thing with some of the DFS/ADFS chips that I've seen,
a disc of one type would be recognised even if the other filing system was
selected. I don't think that they shared any code though.
IMHO it would be difficult if not impossible to integrate the code into a
single 16k ROM, if it was possible it would have been done by now.
Jonathan Graham Harston (jgh@...) suggested that he might be
considering writing an ADFS / DFS replacement for the BBC Master that might
be incorporated into a later OS for the Master (replacing 3.2 not 3.5 as far
as I know). He suggested that it should also include HADFS and DOSFS.
I hae no idea if he has any plans to develop this idea but he does have
experience writing filing systems.
>I would envisage the HDDFS to be a replica of ADFS with the added bonus of
>being able to write 1.44mb disks, so perhaps just ADFS and HDDFS could be
>put together?
Perhaps it would be wise to implement the ADFS D (800k), ADFS E (800k) and
ADFS F (1600k) formats that the later Acorn computers use it would certainly
be a much better than inventing a new 1440k ADFS.
---
You may want to consider making the HD drive accesible via the 1Mhz bus with
the hardware for controlling the HD drive in an interface between the drive
and the computer. (Like a hard drive.)
The ADFS already present in the Master (for example) already contains the
code to access hard drives so you'd just format the disc to 1600k (or
whatever) and hey presto you have a high density drive on your BBC.
This would mean that you wouldn't need to change anything inside your
computer, you'd just need a 1770 drive interface and ADFS. All BBC Masters'
have this anyway. And upgrades fairly easy for BBC B, BBC B+ owners. (I
think some Masters have a 1772 interface but it makes no difference AFAIK.)
You would need no new filing system ROMs (a high density DFS is not
practical).
You could write a filing system to access DOS discs that are in the HD
drive, any existing programs that use DOS hard drives over the 1Mhz bus
should work without modification.
What do you think?
Jon Ripley
e-mail - jonripley@...
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