22 Aug
2006
22 Aug
'06
3:08 p.m.
Well, the keypad was terrible (I ended up soldering 20 switches from
Maplin onto the MK14 PCB, the holes and traces were there for them...).
There were some very marginal bits of logic design (hint : a '157 is a
multiplexer, a '175 is a latch, but the MK14 uses the former as a the
display output register. It works for _some_ makes of '157...). The CPU
buses are not broungt off-board, so expansion was a pain.
Hmm, that is really surprising about the (lack of) expansion ability - I would
have thought it's one of the primary reasons in choosing a machine of that
class. I can't imagine doing something like in the ZX series (solder-pad edge
connector) would exactly have put the manufacturing cost up by much! And so on. I
wish I'd saved a little more money and bought an Acorn System 1.
True - at least there was the ability there to re-use the CPU card and add a
eurocard lack later along with all the later System cards. Mind you, from
memory of Acorn ads they didn't really play up any future expansion ability -
I don't think Acorn saw it as a real selling point back then. Releated to this was a horrible bit of Torch
design. As you may know,
Torch sold an upgrade for the BBC micro which added an internal PCB
containing a Z80 running CP/N (no, that's not one of my typos...). The
Beeb power supply couldn't really supply that as well, so what you did
was remove the Beeb PSU altogether, connected a cable to the power
connections on the Beeb's mainboard, and run the whole thing off a PSU
in the (Torch-supplied) disk drive unit.
You know, my prototype Torch Z80 disk unit has power out at the back; I can't
remember whether the production ones were like that or not. It had never
occurred to me that someone would want to power the machine from it!
In a way I'm surprised that the beeb PSU couldn't cope though - the current
draw can't be a lot worse than other various internal add-ons for the beeb.
I've certainly seen a lot of beebs running the Torch copro without any PSU mods.
YEs, but that wasn't 'offiical' either. IIRC Acorn specifically fobade
you to run anything off the Beeb's PSU. I think Torch tried to do things
properly.
-tony