Sinclair ZX80 questions

[Jules Richardson]

Tony Duell wrote:
>> Tony Duell wrote:
>>> I bought an MK14 back when it was current. That put me off Sinclair for 
>>> life...
>> Out of interest, what was so bad about them that wasn't typical of that class 
>> of machine around that time? Admittedly without having been involved at the 
> 
> 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.

cheers

J.

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