🚀 go-pugleaf

In article <1b3506INNjc4@swan.doc.ic.ac.uk>, mybg@doc.ic.ac.uk (M Y Ben
Gershon) writes:
|> 
|> Does anyone know of any way to have more than 4 expansion cards on an Acorn
|> RISC computer (540 in my case)?  I recall reading that it cannot be done
|> directly (ie some form of internal expansion which would allow more than 4
|> cards to be USED simultaneously), due to OS limitations, and
assumptions made
|> by various card manufacturers about the address mappings used by the
4 'basic'
|> cards.
|> 
|> What would interest me would be an expansion which allowed, say, 2
additional
|> cards to be added, with some form of physical switch to toggle between them
|> and two of the 'resident' cards.
|> 

Well there's no technical reason why you couldn't, but I wouldn't advocate the
ability to switch between them while running.  Between resets maybe.

|> Has anyone got any ideas?  I am not an electronics buff, so I
wouldn't be able
|> to build anything, but maybe someone out there is developing something... I
|> am getting absolutely desparate, as I have 4 cards installed, but two newly
|> released cards also seem very interesting!
|> 
|> Michael Ben-Gershon

Well, relatively simple, there's usually a spare input on the 4 line decoders
in most circuits due to the large number of enable signals supplied (although
you can find a use for all at once, so Acorn may have done) but it would be
trivial to build the address decode logic to allow for this.  My worry would be
just how far you can take signals away from the motherboard.

Ian Griffiths