A Sinclair ZX80 replica kit no
Posted by Stunning-Produce8581@reddit | vintagecomputing | View on Reddit | 37 comments
Hello everyone,
I’m thinking about making some ZX80 kits, complete with PCB, components, psu, 3D printed case, replica stickers, replica keyboard overlay, replica manual & assembly manual.
But to get an idea, I would like to now if such a project is interesting. The idea is to sell kits like they did in 1980. Pre programmed eprom etc… so it’s easy to make for everyone. The idea is to sell it for €199,99. (Still a first assumption)
Fun fact, the kit was sold for 79,99 pounds back then. €199,99 nowadays is equal to (+-)35 pounds if it was sold in the 80’s.
I try to make it as cheap as possible and still make a some money out of it. The goal is not to make a lot of profit, but to make a nice kit that can be bought by everyone, also people who like to build such a computer, but without the time or knowledge to do it from “scratch” Of course we need to make som profit to make it cost-effective.
Pleas let me know if something like that sound interesting.
The picture is of course from a real one from internet.
g-4-t@reddit
This one just appeared on Ebay. With original white power supply. That's a must for the enthusiasts. Do replica power supplies, would be a buy for all existing and new...
https://www.ebay.co.uk/itm/277000877284?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=cBFfKFfVR5C&sssrc=4429486&ssuid=cBFfKFfVR5C&var=&widget_ver=artemis&media=WHATS_APP
Stunning-Produce8581@reddit (OP)
That’s really cool. A 3D printed case would be the easiest way. Getting it all molded would be the Cooles option, but way more difficult. And the dimensions have to be available.
g-4-t@reddit
Take a look at this https://sinclairzxworld.com/viewtopic.php?f=8&t=4639
m-in@reddit
It will probably be based on a small FPGA, since it’d be the cheapest - smallest PCB, ability to connect an HDMI (ahem, DVI) monitor or a VGA monitor or a composite video monitor. Probably could also interface to a USB peripheral or two - say a printer, joystick, or mouse. All that would fit into an FPGA and provide good user experience.
If you want to sell literally the exact replica, then it will cost more than it has to, and without the ecosystem of peripherals it will be worthless for most. Just off the top of my head: various memory expansion modules, thermal printer, analog/digital I/O etc. Even analog interface to a tape recorder is problematic - it would need to be probably a USB audio device so it can record into and play back from any mobile device or laptop.
The lack of expansions will be the biggest barrier to adoption. Without them, this is a paperweight more or less. I had a ZX81, printer, a memopak (RAM), a digital I/O and ADC interface box, and a few other things I forget. Maybe joystick interface.
So, yeah, to make this fun and usable would take a small FPGA that has the CPU, RAM, all the interfaces, a couple USB connectors - some type A, some type B, edge connector interface with gold plated fingers, and some video outputs and cassette audio for those that have a real tape recorder handy.
It would also be nice if the serial flash that has the FPGA bitstream could be used as a built-in disk drive.
Direct replicas that need a whole ecosystem to exist around the product - like it did back when it was originally marketed - do rather poorly without said ecosystem in place. It’s just no fun. Supporting a USB thermal printer would be a good start in bringing back the original experience in a way, but there’s more to it of course.
ElevatorGuy85@reddit
If it doesn’t make the screen flash every time the keyboard is pressed, I’m not interested!
/s
m-in@reddit
Yeah. 1:1 experience is fine, but the base computer is never enough for most things.
Stunning-Produce8581@reddit (OP)
Thank you for your extensive post! I think I get what you mean. You are right about the fact that without peripherals you can’t do much. I will think about that. The idea is to sell replicas that are as close as possible to the original. Aiming at the people who like to make an old computer kit like it would be back then. But this idea is because I would like such a kit. I collect old computers. Not do a lot with the software, but because I like how they look and the hardware that’s inside (still understandable), to work with floppy sore cassettes. And because it’s fun. I personally would not buy a modern z80 computer because I just like how the originals were and I personally won’t have that much fun if it would be a new kit. But that’s very personal. So I appreciate your ideas, and take it with me, because a sort of ‘semi option’ would be kinda cool I think.
m-in@reddit
Find a thermal printer mechanism available for purchase and offer a kit for that too then, if you can. And a memory expansion kit. I can probably find someone who could rewrite the ROM to be mostly binary-compatible where it matter, but in a white room environment so no copyright infringement. The rom isn’t long anyway, only goes to 1DFFh on ZX81 so maybe even less on ZX80.
Stunning-Produce8581@reddit (OP)
Thanks for sharing the possibilities, I will do some research via the internet. Unfortunately I have not found audio files like for the apple II, there you could connect your phone to load programs. Maybe it would be possible to make a sort of cardrige with an eprom. I found something about the ROM though:
"I also recommend you read this document. Sky who bought Amstrad (who bought Sinclair Research) do not own the ZX80 ROM or ZX81 ROM copyright. So in terms of copyright of the ZX80 ROM or ZX81 ROMs, it’s a grey area."
https://sinclairzxworld.com/viewtopic.php?t=3514
scubascratch@reddit
This is a neat idea but are you sure the components are still source-able? The Z80 probably easy to find but are the ram chips? Did ZX80 use a video chip or was it hand rolled like Apple II?
Stunning-Produce8581@reddit (OP)
Thanks! I think it would be fun to build such a replica. In general, the components are still availible, but research needed to find everything. The explanation about the video has already been done ;)
Sample_And_Hold@reddit
There was no video chip. The screen was just a single plane of 24 lines by 32 columns of 8x8 bit-mapped characters and it was all generated by the CPU. That's the reason the video flickered so much, since the processor had to interrupt the video signal to do other things.
scubascratch@reddit
Right - wasn’t there some “fast mode” that turned off screen updates?
Was the video bit banged?
Sample_And_Hold@reddit
Yes, "fast mode" was the one with the flicker (caused by all the switching off) and it was the default on the ZX80. "Slow mode" (introduced on the ZX81) allocated most of the CPU time for the display, releasing it only during the vertical refresh cycle (i.e.: in-between video frames), in order to eliminate the flicker (and it slowed everything else down as a consequence). There was a hardware hack known as "why wait", which could speed up slow mode by about 10%.
kimondo@reddit
There is a very good kit called the Minstrel - fits in an existing case or can be used with its own (better) keyboard https://z80kits.com/shop/tynemouth-minstrel-3/ - it’s compatible with both zx80 and 81 software including 3d monster maze. I think the version 3 also includes the fix to the video output that the original lacked.
Stunning-Produce8581@reddit (OP)
That is a nice kit! you can do more with that one indeed.
Suspicious-Ad-8474@reddit
Another one I found https://www.pcbway.com/project/shareproject/ZX80_SINCLAIR_REPLICA_066e073d.html
Stunning-Produce8581@reddit (OP)
Interesting! The Rom improvement is very handy.
SirTwitchALot@reddit
Fun idea, just make sure you have the license for the ROMs. It's easy to think that no one cares about something so old, but if you're project becomes large enough, whoever owns the copyright currently may come out of the woodwork
Stunning-Produce8581@reddit (OP)
Thanks! That is a good point!
Suspicious-Ad-8474@reddit
I think amstrad owns the rights to all classic spectrums computers
Stunning-Produce8581@reddit (OP)
Yes, and then “Sky” I read somewhere. It is discussed in this topic: https://sinclairzxworld.com/viewtopic.php?t=3514. I don’t know if patented stuff need to be renewed after time.
Suspicious-Ad-8474@reddit
Patents protect inventions, processes, and designs. Copyright protection typically lasts for the life of the author plus 60 years. So depending on the part of you can get hold of a zx80 plus a manual you might get the patent numbers so you can look them up
Stunning-Produce8581@reddit (OP)
Ah okay, then i mixed it up. Thanks. I will check it out.
Glidepath22@reddit
IF and only IF you were able to at least plug a standard keyboard into a USB
Stunning-Produce8581@reddit (OP)
A fair enough thought. Will think about this possibility!
Stunning-Produce8581@reddit (OP)
A fair enough thought. Will think about this possibility!
theLightSlide@reddit
I would absolutely buy something like this as a gift for my husband.
Stunning-Produce8581@reddit (OP)
Thanks for letting me know!
RandomJottings@reddit
It’s certainly something I’d be interested in
Stunning-Produce8581@reddit (OP)
Thanks for your reply! I appreciate it
JewelerAdorable1781@reddit
I'll take one, I like it.
Stunning-Produce8581@reddit (OP)
Thanks for letting me know!
retardedboi1991@reddit
I'd be interested, i do love a good soldering kit and i'm salty i missed out on the gigatron a while back.
Stunning-Produce8581@reddit (OP)
Thanks for your reply! The gigatron? I have missed something 😅
retardedboi1991@reddit
8 bit guy did a video on it ages ago and by the time i was a competent solderer it was out of production.
It was basically a micro without a microprocessor so it all ran on TTL(?) logic and it came as a kit.
Stunning-Produce8581@reddit (OP)
Oh, I think I remember lmao. I have seen it I think.