How many computers?

From: Pete Turnbull <pete_at_dunnington.u-net.com>
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,
apparently.
>
> 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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