Date   : Sat, 23 May 1998 13:05:31 BST
From   : Chris Thornley <osu036@...>
Subject: High density

If you change two jumpers on the bbc circuit board so it is set of 8inch
drives this doubles the clock pulses 
going to the disc controller but you have to write a filesytem that can uses
HD discs. Also timings are shorter 
as the chip running at twice its rate. ie 6ms access speed now equals 3ms.
8 inch drives as far as I am aware are high density. The two jumpers are
mentioned somewhere in the 
hardware refernce manual. A similar sort of speed modification people have
done on Atari ST who use 
WD1773 chip which is esentailly the same and TRS80s which either uses wd1773
or the older version of the 
chip. I`ll see if i can find the ST modification details on HENSA.

Bye
Chris
On Fri, 22 May 1998 23:14:56 +0100 Crispin Boylan wrote:

> From: Crispin Boylan <viewtronix@...>
> Date: Fri, 22 May 1998 23:14:56 +0100
> Subject: [BBC-Micro] Ideas on new hardware
> To: bbc-micro@...
> 
> Hi
> 
> You may remember some ideas I was throwing around about High Density disks
> with the beeb, ages ago, I've been doing some more thinking, and have come
> up with this complicated but interesting (I hope) idea:
> 
> So, the idea: would it be possible for a new hardware board to be made
> available for the BBC which allows it to do high density writing?  I
> thought this would be a great idea, as with the ever decreasing
> availability of 5.25 disks and also double density 3.5 disks, why not allow
> the beeb to use high density?  As far as I can think of, and I have done
> extensive reading about what you can and can't do with the BBC, there is no
> major stumbling block.  One thing I have come across is really an
> indecision, which Floppy Disk Controller to use!  You may or may not know
> that some FDC's can only read, not write, single density, which is bad as
> most beeb disks are single density (well all the DFS ones).  So, I decided
> that maybe the Western Digital 37C65 which can write single and double and
> high density disks would be the solution.  Is this, to everyones knowledge
> a good choice?  Would another FDC be suitable, I had in mind the Intel
> 82078 but I cannot get enough specs on this device to make a complete
> analysis of its capabilities.
> 
> I know there are people out there more knowledgable than me (like most of
> you :) ) who like designing hardware for the beeb, so I am asking you this
> to see if you think it is possible/feasible.  I could just about manage to
> cobble together some hardware with a little help from various people (any
> offers!?) but software I am completely stuck on, i have little knowledge of
> programming DFS's, and as far as I can see a new DFS, ADFS and HDDFS (High
> Density DFS, nifty eh?) would need to be programmed. Know any good
> 'DFSers'?  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.  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?
> 
> Cheers,
> Crispin Boylan - viewtronix@...
> 
> SWOS Page - http://easyweb.easynet.co.uk/~viewtronix
> BBC Micro Games Archive - http://easyweb.easynet.co.uk/~viewtronix/beeb/
> 
> "I am, I am Superman, and I can do anything " - REM

               />      Christopher J. Thornley is OSU036@...
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