Grid 1520

From: Pete Turnbull <>
Date: Sun Dec 12 13:33:06 2004

On Dec 12 2004, 17:58, Philip Pemberton wrote:
> In message <>
> Brian Mahoney <> wrote:
> > Tandy used roms in some
> > of their models, didn't they? I mean to store applications. Acorn
> > I think.

Yes, the BBC Micro (and 8-bit successors) couyld use "Sideways ROMs",
ie ROMs mapped into the same address space as BASIC, and switched in
and out by the O.S. Archimedes (32-bit) machines and successors could
have ROMs on expansion cards (eg an Ethernet card might contain the
card drivers and TCP/IP stack).

> Sounds like you're referring to the "5th Column ROM". All the Acorn
> I've seen have RISC OS in ROM anyway (No HDD? No problem!), though.
> The 5th Column ROM socket was - IIRC - fitted to all the Acorn
> machines up to the A5000. I don't think there was much that ever used

There's no "5th Column ROM socket". Even the term is a invention of
someone outside Acorn. What they mean are simply Extension ROMs on
expansion cards, which contain relocatable OS modules which get copied
into RAM when the machine is booted. (It has to be, most ROMs are only
8 bits wide, but the memory bus is 32 bits. Obviously you could use
four ROMs, but I never heard of anyone doing so, although the spec does
allow for it.) Almost all Ethernet cards, several SCSI cards, scanner
cards, and several others, use them. The only one I know of that could
contain application software that wasn't tightly bound to some
interface on the same card, was Computer Concepts card for
Inter<whatever>, which was a bit of a flop. It was only useful for the
BBC Emulator, and the code still had to be copied to RAM to be

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Sun Dec 12 2004 - 13:33:06 GMT

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