Date   : Sun, 24 May 1998 15:35:58 +0100
From   : Theo Markettos <bbc-list@...>
Subject: Re: Ideas on new hardware

In message <3.0.3.32.19980522231456.006b7dc8@...> you wrote:

> Hi
> 
> 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?

In theory, I don't why not.  There could be problems getting the require
1Mbit/s to the controller, but I think it should be able to manage this,
perhaps by connecting it to the 2MHz system bus instead of the 1MHz bus.

> 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?

Make sure you get a controller with a '765 core - as most modern controllers
have - so the software would more or less run on any '765 core device.  AFAIK
both the WDC37C65 and the 82078 have this core (the 82078 also has 2Mbit/s
features for writing 2.88MB floppies).

> 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.

The datasheet used to be at http://developer.intel.com, but I don't know if
it's still there - I've got a printout of it here, but lost the original PDF.
According to the datasheet it will do 250, 300, 500 Kbps and 1, 2 Mbps - so
if 1Mbps is high density, then 500Kbps is double density and 250Kbps is
single density, so it should work.

The 82078 supports a fair number of other features like powerdown for
notebooks and soft-swappable drive numbers.  It also comes in a 44 or 64 pin
QFP package, which you might have trouble soldering to (I've wirewrapped 100
pin QFPs, so it's not impossible).  The 37C65 comes in a 40 pin DIP IIRC,
which is a much nicer package.

If the Beeb can handle the bus speed, you could also consider faking enough
of an ISA bus to be able to plug in a cheap PC IO card - you'd also then have
serial, parallel and IDE slots thrown in free.  For more info on the ISA bus,
have a look at the alt.comp.hardware.homebuilt FAQ.

> 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?

For tips for the software, you might try Jonathan Harston
(jgh@...) - IIRC he wrote HDFS for the Beeb.

Let me know if you'd like more info on the 82078.

Hope this helps,
Theo

-- 
Theo Markettos          Home:   theomarkettos@...          
Liphook                 Work:   marketto@...                     
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UK                      Web site, including Acorn backup software
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