21 Aug
2006
21 Aug
'06
1:38 p.m.
On 20/8/06 13:30, "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
wrote:
I've got a ZX80 here (issue 2A) which has a keyboard overlay attached that
looks very like that of a Sinclair ZX81.
That's because it is :)
The ROM in the machine is dated week 16 of 1981, and
carries the marking
C77018, and a 1981 copyright.
Is this a machine that's been subjected to a ZX81 upgrade kit or something? I
wasn't aware that such a thing existed.
Yep, the 'enhanced' ZX80 ROM was released before the ZX81 hit, as well as
allowing frustrated ZX80 owners to upgrade their machines afterwards too. I
*think* that's the right way round, I can remember ads for the ZX81 that
also featured ROM upgrades for the '80.....
ZX80 legend underneath. However, two black
press-fittings attach it to the PCB
at the corners of the front edge - are these press fittings there on all
ZX80s, or have these been added in order to secure the overlay in place?
They're on all ZX80s:
http://www.binarydinosaurs.co.uk/Museum/Sinclair/zx80/
The machine came with a "ZX 16K RAM" module
(red lettering) which I assume is
later and more in keeping with a ZX81? Separately though I do have a module
marked as "ZX80 16K Byte RAM Pack" (white lettering). Question is, are they
interchangeable and the lettering was altered - or does the ZX80 variant map
They're interchangeable, indeed I use a ZX81 RAM pack with my ZX80 and it's
fine. The white lettered RAM pack is rarer than the red lettered one from
what I remember.
I've also got a ROM marked as: "ROM contents
copyright 1980 Sinclair Research
Ltd" - is this the original ZX80 ROM (and the ROM in the machine is an
upgrade), or is this likely something else entirely?
It's the original ROM - the upgrade was fully removable for some reason,
simply undo the ZX81 overlay and put the old ROM back in. I can't imagine
why anyone would want to do that, but I'm pleased that you can!
Curiously there are a few stray fibres glued to the
underside of the PCB -
presumably these are a left-over of cheap PCB manufacture and Sinclair's
horrible quality control! :-)
Did they ever have any?
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?