How many computers?

From: Pete Turnbull <>
Date: Sun Jul 19 06:12:32 1998

On Jul 18, 22:53, Tony Duell wrote:
> Subject: Re: How many computers?
> > My friend reports that the Graduate doesn't have a BBC ROM, and indeed
> > doesn't use the Tube. It uses the 1MHz bus to access BBC I/O,
> You know, I thought I remembered it having a 34 pin ribbon cable. (1MHz
> bus, not Tube).... Time to dig it out and experiment.
> How on earth does the Beeb know it's there, though, without a ROM.
> Acorn's MOS (the Beeb ROM OS) doesn't look for peripherals on the 1MHz
> bus, surely?. I can't believe it needed a BBC disk as well...

Yes, I find that very odd too. The address lines, page selects, and R/W
signals on the 1MHz bus are unidirectional (direction: out of Beeb) so
about the only things the Graduate could control would be the NMI, IRQ, and
analogue input lines.

Pete						Peter Turnbull
						Dept. of Computer Science
						University of York
Received on Sun Jul 19 1998 - 06:12:32 BST

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