Date : Mon, 23 Jul 2007 16:34:14 +0100
From : jgh@... (Jonathan Graham Harston)
Subject: modern BBC remake
>Message-ID: <4f0677a313info@...>
Sprow <info@...> wrote:
> > > External tube connector configurable as either an IDE interface or
> > > Tube
> >
> > Why either? They aren't mutually incompatible.
>
> Because for it to fit a normal BBC B/B+ case it must use all the existing
> holes. The external Tube connector has 40 pins, so does an IDE port, so it
> makes sense to multiplex them. An internal Tube connector like the Master
> has still allows for a coprocessor.
Ah, it hadn't sunk in that people had suggested putting it inside
a standard BBC case. I was still picturing it as a beefed-up
MiniBeeb, maybe a box the size of the A9 (2l ice cream tub).
Anyway, if I'm going to have a hard drive, I may as well mount it
inside the case, so an internal IDE connector and an external Tube
connector can co-exist.
> Is there an internal Z80 coprocessor or had Acorn given up on the Z80 by
You can mount the external Z80 CoPro internally, plugging it into
the external Tube connector and wrapping the ribbon cable inwards.
I had my Z80 inside my only (at that time) Beeb like that while I
was in Hong Kong.
> > Surely it's going to be slow as mole-asses to actually use for anything
>
> I proposed a 14MHz 6502, plus where compatibility is less important (ie. not
> games that poke the video RAM directly) the video RAM doesn't need to share
> time with the CPU on the main bus - it can be in a 'shadow' RAM area say 32
> bits wide. Indeed, the 6845 replacement could accept VDU sequences directly
> rather than relying on the MOS to go poking the screen,
That's my thinking also. As any screen mode larger than 20K
wouldn't be able to fit where traditional programs would expect
the screen memory to be, there's no reason why a different access
method must be used. My scribbled notes from way back have a
system accessible through a byte-wide port that you send VDU
sequences through, and another port for sending queries through,
such as OSBYTE 135, OSWORD 9, etc. Effectively, it looks like a
Tube host to the system talking to it :)
--
J.G.Harston - jgh@... - mdfs.net/User/JGH
Jet Set Willy Resources - http://mdfs.net/Software/JSW