
Minstrel ZX80 Clone - sohkamyung
http://blog.tynemouthsoftware.co.uk/2016/12/minstrel-zx80-clone.html
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Theodores
No 3D Monster Maze - well, that is a disappointment!!! That was my favourite
game on the ZX81 and it actually was terrifying to bump into him even though
the screen was very blocky pixels with a very slow refresh rate. We are
talking seconds per frame.

I am also amazed that you can buy a replacement ZX80 keyboard. This required
someone out there to know what it was and to bother to put it on ebay etc. for
someone else to find. This is trade at its most obscure, yet this is also our
key survival skill - trade. It is what enabled our variation of the human form
to survive ice ages where other human varieties perished. We could trade, they
could not. Once we traded in things like salt, nowadays it can be in anything
including a ZX80 keyboard.

The UHF modulator was replaced in this article, the original modulator was
ubiquitous and found in all computers of the era that needed a TV for the
monitor. At the time this part was taken for granted, however, it was the
component that enabled the home computing revolution, without it and screens
would have been an extra £400 or so (as per BBC/Acorn monitor). There must be
more information out there on how these UHF modulators came into being.

~~~
timthorn
> I am also amazed that you can buy a replacement ZX80 keyboard

There's a thriving scene for retro computing in the UK - looks like that is
the primary business of the creator. I assume that the (non-test) keyboard,
ULA and case all came from a donor machine. After all, there's the link to
"Send me something interesting to repair / review / reuse / recycle"

[http://rc2014.co.uk/modules/universal-micro-
keyboard/](http://rc2014.co.uk/modules/universal-micro-keyboard/)

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jaclaz
Just for the record, and for those not familiar with these, the original ZX80
and ZX81's had only 1 Kb memory.

The "expansion" to 16 Kb (and later to a whopping 64 Kb!) was an extremely
costly "add on", it was a small "vertical box" attached to the rear end
connector (and the connection was - to say the least - flaky):

[http://www.computinghistory.org.uk/det/34163/ZX81-16K-Byte-R...](http://www.computinghistory.org.uk/det/34163/ZX81-16K-Byte-
RAM-Pack/)

An image of a ZX81 with the expansion box mounted is here:

[http://oldcomputers.net/zx81.html](http://oldcomputers.net/zx81.html)

~~~
Joyfield
That would be kB (kilobyte) and not kb (kilobit) or Kb (kelvinbit).

~~~
quirkafleeg
What's a "kelvinbit"?

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WorldMaker
Now I want to see someone derive a nice formula that results in a kelvinbit.
Offhand, I'd guess something to do with information entropy in temperature
sensitive media. (Entropy rather than density as that would be more along the
lines of bits/kelvin I'd assume. Or heat output would be kelvins/bit.)

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mmastrac
This might be a cool project to build at Seeed. I think they could populate a
board with sockets, SMD resistors, jacks and switches, leaving just the chip
insertion for the end-user.

Caveat: I've only ever had them build an unpopulated through-hole board for my
one hardware project.

~~~
pjc50
Parts availability might be a serious problem, especially the ULA.

~~~
tynemouthsw
That's the point of this clone, it's based on the ZX80 which uses only
standard TTL chips, all of which are still available today. The original 1K
RAM chips and mask ROM are not, but modern parts have been substituted. The
next version will incorporate an NMI slow mode circuit which will make it
fully ZX81 compatible, still only using standard TTL parts.

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Graham24
The ZX80 was the first computer I touched and used and it was bloody awful.

I mean really, you press a key and the screen blanked out as I recall.

Didn't stop me from getting the far superior Vic-20 the following xmas.

~~~
Angostura
The ZX81 had the revolutionary ability to support both screen refresh, and
keyboard input simultaneously! Well - as long as you didn't engage 'FAST' mode
- which made your FOR NEXT loops go super-fast, at the expense of blanking the
screen.

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rwmj
Can anyone explain what he means by "I have replaced [the UHF modulator] with
the single transistor composite video buffer" ?

~~~
nickcw
On the original ZX80 it produced modulated RF to connect to your TV aerial
socket as it wasn't common then to have any other inputs on TVs.

More modern TVs have a composite video input which makes the RF modulator
redundant. The quality of the picture is much better via composite video.

In fact that is how I used to use my ZX80 back in the day with a wire clipped
onto the input to the RF modulator connected to a 9 inch monitor my dad
liberated from work!

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digi_owl
Articles like this one makes me wonder if dad's ZX81 clone is still sitting in
the basement.

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rwmj
Your dad cloned a ZX81 or he has another company's clone of a ZX81?

Tangentially related: The Jupiter Ace was a relative of the ZX81 (same
designers, different company) which ran FORTH instead of BASIC. If anyone has
one they are worth a lot of money because it seems fairly few were made and/or
survived.

~~~
teh_klev
If digi_owl's dad is/was resident in the US or Canada it could have been a
Timex branded version of the ZX-81. There were also quite a few clones back in
the day:

[https://en.wikipedia.org/wiki/List_of_ZX80_and_ZX81_clones](https://en.wikipedia.org/wiki/List_of_ZX80_and_ZX81_clones)

~~~
pjmlp
Timex clones were also sold in the Iberian peninsula.

I had a 2068.

