More than 4 expansion cards ??

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3 total messages Started by M Y Ben Gershon Fri, 09 Oct 1992 05:23

#273

Author: M Y Ben Gershon
Date: Fri, 09 Oct 1992 05:23

18 lines
1376 bytes

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.

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

Re: More than 4 expansion cards ??

#277

Author: David Elworthy
Date: Fri, 09 Oct 1992 14:09

12 lines
864 bytes

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)?

No, you can only get 4 in the case! The other 536 will have to go
somewhere else!

-- david

(Sorry - thesis writing makes your brain go all funny.)

Re: More than 4 expansion cards ??

#281

Author: I.D. Griffiths
Date: Fri, 09 Oct 1992 15:12

37 lines
2093 bytes

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

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