Date   : Wed, 19 Oct 2005 22:05:35 +0100
From   : Jon Ripley <jon@...>
Subject: Re: Dual Floppies On A Master

Jules Richardson wrote:
> Jon Ripley wrote:
> 
>> When using a cable with a twist you need to set both drives to be 
>> drive one.
> 
> Can the beeb address four drives, or just two? I honestly can't 
> remember. IIRC the 8271 *should* be capable of it, but I think you end 
> up doing some of the work in software and I'm not sure if the beeb's ROM 
> code does this or not...

You can only have two physical floppy drives connected to a Beeb at any 
one time, to have more connected you will need to employ some sort of 
hardware switch to ensure that only two drives are active at any time. 
The power supply is not capable of powering more than two physical 
drives at any given time - some older Beebs had trouble with powering 
only one drive.

Using two physical drives:

With ADFS you have drive 0 and drive 1, each being a seperate physical 
drive.

With DFS you can have four logical drives, drives 0 and 2 are the first 
and second sides of the first physical drive and drives 1 and 3 are the 
first and second sides of the second physical drive.

HTH,
Jon Ripley
-- 
http://jonripley.com/
Winner of the 2004 and 2005 Classic 2k Classic Text Adventure Competitions