18 Jul
1998
18 Jul
'98
11:12 p.m.
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