Date   : Sun, 26 Apr 2009 23:01:31 +0100
From   : adsb@... (Andrew Benham)
Subject: ADFS Drive Numbers

Ian Wolstenholme wrote:
> Is there a version of ADFS which can access drives numbered 2&3
> or 6&7, or is there a hardware limitation preventing this?

I've never heard of an ADFS version supporting this.  On the Master
circuit diagram, a third floppy drive select signal is shown, but
the components to achieve this aren't fitted.

> I've just been jiggering about with the Technomatic and if I set the actual
> disc to anything other than 0 or 1, the controller won't recognise it, and if
> I set the controller to anything other than 0, ADFS won't access it (although
> in this case the "Not found" error does go away if I try *MOUNT 2).
> 
> If I were to happen to connect up two separate Winchester units, daisy
> chaining them together (eg. to make a backup of the Technomatic!!)
> what would I need to do to the drive and controller IDs?  I just had two
> Winchesters on the Technomatic Adaptec controller, both set to 0 and
> that gave some very funny results! It worked OK with one drive as 0 and
> the other as 1, but I don't know what would happen if I put another
> Adaptec controller on the 1MHz bus, since changing the Technomatic's
> Adaptec ID doesn't seem to let me access it.

One host adaptor can drive one Adaptec bridge board, and the bridge
board can drive two ST506 hard drives (daisy chain the 34-way control
connection, use unique 20-way data connection per drive).  I've backed
up my BBC Winchester like this in the past.

If you wanted to connect two separate BBC hard disk units, you'd need
to change the address block that one of the host adaptors used on the
1MHz bus.  On the host adaptor circuit diagram I have, a jumper is shown
that allows a different address block on the 1MHz bus.  However the host
adaptor I use doesn't have such a jumper - it would be a case of cutting
a track and wiring to a different point.
Having done this, you'd need an ADFS that could cope with two host
adaptors on different address blocks - and I don't believe such a beast
exists.

-- 
Andrew Benham         adsb@...       
Southgate, London N14, United Kingdom

The gates in my computer are AND OR and NOT, not "Bill"