The 40-Year-Old Version: ZX81's sleek plastic case shows no sign of middle-aged spread
- Reference: 1614950351
- News link: https://www.theregister.co.uk/2021/03/05/zx81_at_40/
- Source link:
Released on 5 March 1981, the [2]ZX81 was the successor to 1980s [3]ZX80 and, like its predecessor, was based around a Z80 CPU. Both machines also featured 1KB of memory and required a UHF television to display the monochrome output.
[4]
[5]
Rick Dickinson shared this sketch on [6]Flickr , explaining it was "how I imagined the ZX81 to be an expandable range of boxes following a vaguely modular approach with a common width." [7]Pic: CC 2.0
The ZX81 was, however, a far sleeker affair than its white plastic-encased stablemate. A Rick Dickinson-designed case made for a more consumer-friendly computer, even if the pressure sensitive membrane of the keyboard was somewhat less easy to use.
[8]
[9]
Click to enlarge
The computer came in kit form for a hair under £50 or ready-built for £69.95 and could, if you were fortunate enough to find one in the early days, be picked up from UK high street stores such as WH Smiths, whose [10]advert at the time enthused: "You'll be surprised at how much you can do with a personal computer and even more surprised at how little it costs."
Its lack of colour graphics, sound or storage compared to other hardware launched in 1981 paled into insignificance when one considered the prodigiously low price.
[11]
Click to enlarge
Memories
Raspberry Pi founder, Eben Upton, told us: "The ZX81 was the first computer I ever owned," before admitting that he never managed to get his hand-me-down computer to display anything on the screen – doubtless another victim of Sinclair's drive to keep costs down on the connector front.
Man recreates ZX81... in Lego [12]READ MORE
Founder of the Centre for Computer History, Jason Fitzpatrick, also recalled the plastic slab being his first introduction to the computing world and constructing it from kit form with the aid of his father: "I can't remember how long it took to get it [the kit]," he told us, "but it was more than the time they said in the advert!"
"It was a kind of crowdfunding before crowdfunding existed," he said in reference to some of the challenges faced by consumers in getting hold of the hardware they'd paid for.
In spite of the clear limitations of the machine, "we made it do quite a lot," Fitzpatrick recalled, "and it didn't really matter, in my opinion, it didn't matter what it could do. It was kind of irrelevant. And I've got a feeling to Sinclair as well, it was kind of irrelevant what the thing could do. It was for a lot of people, their first introduction to computing and what a personal computer would be."
Fitzpatrick recalled the excitement of the era, the tapping in of code printed in magazines and of game cassette inlays featuring visuals of which the humble Sinclair was patently incapable. He also remembered the pain of persuading peripherals to work, notably the infamous 16KB RAM pack.
"The ZX81," he said, "was a machine built to a price."
[13]
Click to enlarge
It had some simple sockets on the side, but for the real fun an edge connector was exposed at the rear. "For something like RAM, that's not the best way to connect it," Fitzpatrick understated. Some dealt with the RAM pack with the assistance of blu-tack, others, like Fitzpatrick's father, crafted a strap-like affair to stop the notorious block from flapping around and causing an undesired reset.
Wobbly connector aside, Upton also paid tribute to the design ethos of the Sinclair hardware, noting that while the Raspberry Pi is often talked about in conjunction with the BBC Micro, "in some ways we owe more to the aggressive 'design to cost' philosophy of the Sinclair machines."
The BBC Micro would launch toward the end of 1981, and the rivalry between Acorn and Sinclair has been well documented over the years, including a dramatization in the form of the [14]BBC's Micro Men .
It is also possible to run up a ZX81 emulator on variety of modern hardware. The $4 Pi Pico [15]has been spotted doing BBC Micro emulation and The Register understands that something for Sinclair fans is on the way.
You can't beat the real thing, however. Fitzpatrick pointed out that the Centre for Computing History had a number of the devices, including some featuring creative modifications to overcome limitations like that keyboard. "There's always one on display," he said, "there's never a display without a ZX81."
Describing the computer as a "brilliant" bit of British engineering, the Centre for Computer History's Fitzpatrick enthused: "Just to come up with this idea to say, 'right, we're going to make one of these things, and it's going to be at this price point' was really important."
"Without the ZX81 you don't have the Spectrum. I can't rate it higher in terms of importance."
Volunteer at The National Museum of Computing, PJ, recalled the excitement of commandeering the family TV and, while he never got to sample the delights of the RAM pack, recalled dealing with a dodgy power connector with that assistance of sellotape. "As a result of the many donations from schools," he told us, "over the years TNMoC has amassed enough ZX81s to, as a fellow volunteer put it, 'tile a small bathroom'."
As well as plans for running a home heating system from the device, a number of oddities have turned up including one dubbed 'Bluto'. "This one machine," said PJ, "was so crammed full of expansions we struggled to identify all the various cards connected up."
"This completely self-contained Frankenputer brought together the motherboard, PSU, RAM pack and a mysterious unmarked expansion card. These sat in case that house[d] a full-size mechanical keyboard and printer. There was even built-in cooling." ®
"We would love to know who built this and what it was used for. If that person is out there, we'd like them to know that Bluto is still fully working and carefully stored at The National Museum of Computing."
[16]
Above and below: Frankenstein's ZX81 (click to enlarge.) Pics courtesy The National Museum of Computing
[17]
[18]
Click to enlarge
Get our [19]Tech Resources
[1] http://www.computinghistory.org.uk/det/184/Sinclair-ZX81-Issue-One/
[2] https://www.theregister.com/Print/2011/03/04/sinclair_zx81_anniversary/
[3] https://www.theregister.com/2019/03/05/the_first_zx_spectrum_prototype_laid_bare/
[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/personaltech&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2YEJjqOyLvckks9HCnSuI7QAAAAw&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[5] https://regmedia.co.uk/2021/03/05/rick_dickinson_sketch_zx81.jpg
[6] https://www.flickr.com/photos/9574086@N02/1221488047/
[7] https://creativecommons.org/licenses/by-nc-sa/2.0/
[8] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/personaltech&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33YEJjqOyLvckks9HCnSuI7QAAAAw&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[9] https://regmedia.co.uk/2021/03/05/shutterstock_zx81.jpg
[10] https://regmedia.co.uk/2011/03/04/zx81_6.jpg
[11] https://regmedia.co.uk/2011/03/04/zx81_5.jpg
[12] https://www.theregister.com/2012/01/31/man_builds_sinclair_zx81_historic_microcomputer_with_lego/
[13] https://regmedia.co.uk/2021/03/05/shutterstock_zx81_ram.jpg
[14] https://www.theregister.com/2014/02/14/monitor_micro_men/
[15] https://raspberrypiprojects.com/bbc-micro-emulation-on-a-4-raspberry-pi-pico/
[16] https://regmedia.co.uk/2021/03/05/zx81-1.jpg
[17] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/personaltech&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44YEJjqOyLvckks9HCnSuI7QAAAAw&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[18] https://regmedia.co.uk/2021/03/05/zx81-2.jpg
[19] https://whitepapers.theregister.com/
I was at an exhibition and spotted a familiar UI on a very expensive piece of measuring equipment. They reluctantly admitted that there was a ZX81 motherboard inside the machine as it was a lot cheaper than sourcing and making their own.
Retro-Wreckers
ZX80 = 1980
ZX81 = 1981
ZX Spectrum = 1982
Not only built to a price and worked (sort of) but incredible speed to market. Bigger and better. Whereas the Vega+ (ZX Spectrum knock-off) three decades on took how many years to not appear?
Such is progress ...
Re: Retro-Wreckers
It's a shame they screwed up delivering the ZX83 (QL) because they wanted to continue the yearly cycle.
Re: Retro-Wreckers
The QL had the potential to be a good machine, but the price with FDD was going to be too much so it was saddled with micro-drives, too little RAM and much of the potential of the M68k wasted. Once you made use of the excellent expansion potential (card inside the machine rather than a box hanging off the outside) to add FDDs and memory it was an OK machine - only by then it was too late and too expensive. I had two with a "network" between them just to see how it worked...
EDIT: Prior to the QL, I as a non-Sinclair user so probably should not be commenting on ZX81 articles, my early days were using a Sharp MZ-80K followed by an Oric1 and an Oric Atmos (friends were in the Acorn cam with Atoms, BBCs and Electrons). While I did have the odd dealing with ZX80, ZX81 and ZX Spectrum machines it was the firesale QLs which caught my imagination.
Agreed entirely; in principle the ZX81 isn't that far advanced over the ZX80 — it's a larger ROM, an extra counter and some corresponding logic to trigger WAIT and NMI appropriately — but in practice it's a huge redesign, shrinking all the discrete logic down into a single ULA. The entire machine is four chips: ROM, RAM, ULA, CPU. For 1981 that's pretty spectacular.
... and then rolling that on into the Spectrum just a year later is amazing.
ZX80 basic didn't
IIRC the ARM2 chip in my Archimedes didn't have HW FPU
Different problem. The ARM2 didn’t have HARDWARE FP, but had plenty of space and speed to do it in software.
That was the reason for the larger ROM. The original ZX80 didn’t have space for FP routines in the only 4K of ROM space it had.
Re: Retro-Wreckers
Which basically confirms the adage: wait for version 3. We had a ZX81 and that keyboard was truely awful. It's clear the company was using the cashflow to fund the next version and the Spectrum was a much better machine, but, of course, it was to be the Amiga that became the most successful.
The Planet story has echoes of the Sinclair computers with the Gemini being a nice idea with a few design flaws and crappy software support. I would hope the subsequent versions really do show improvements as my Gemini is now basically just a paperweight.
ZX81 option for Raspberry PI?
Does anyone sell a ZX81 style case for a PI?
Re: ZX81 option for Raspberry PI?
Not seen a ZX81 one, but you can buy Spectrum Pi cases.
Others have 3D-printed their own.
Re: ZX81 option for Raspberry PI?
As a kind-of compromise, I bought myself a PI-400. Turning the PI into a computer-in-a-keyboard-that-you-can-plug-into-the-TV provides me with the perfect blend of 80's nostalgia & 20's tinkering.
Re: ZX81 option for Raspberry PI?
I'm toying with the idea of either getting a [1]Pi-400 , or the [2]Pi-4 desktop kit . The Pi-400 looks nice, but appears to only be available with 4GB RAM, whilst the desktop kit is available with 8, and I'd like to be able to use the Pi for hardware hacking...
[1] https://shop.pimoroni.com/products/raspberry-pi-400?variant=32280738005075
[2] https://shop.pimoroni.com/products/raspberry-pi-4-desktop-kit?variant=31856449290323
At first I thought, "oh great and article about the ZX81", then I thought "OMG 40 years, how depressing!"
"Some dealt with the RAM pack with..."
An article in the Nov-81 issue of Your Computer detailed a great fix for the Ram pack-wobble problem sent in by reader "P.R. Ainsworth of Swansea".
P.R.A., if you're reading this, Thank-you. It worked a treat.
Re: "Some dealt with the RAM pack with..."
One does not simply cite an old home computing magazine in a forum, one has to post a [1]link to archive.org as well.
[1] https://archive.org/details/your-computer-1981-11/page/76/mode/2up
Re: "Some dealt with the RAM pack with..."
Aah, the advert for the (far superior if rather less popular) Microtan hi-res screen takes me back :)
Re: "Some dealt with the RAM pack with..."
Just the talk of RAM pack wobble is doing it for me on the nostalgia front...
Re: "Some dealt with the RAM pack with..."
Just as well Hermann Hauser was with Acorn, as I can imagine this going down as part of their Public Image if he had been with SInclair.
Rampack expansion problems? Jah, Wobble.
Re: "Some dealt with the RAM pack with..."
What catches my eye is the Casio 702p on page 13, was it my brother that had one? But I still have the 3600p which I bought some time later... even, somehow, still with the manuals!
Re: "Some dealt with the RAM pack with..."
I still have my copy of Personal Computing Weekly or something like that with "ZX Spectrum: first look at Sinclair's new micro" on the cover. Nice piece of history.
"crowdfunding before crowdfunding existed"
At this distance that's funny. I rather suspect that it wasn't at the time.
Although Sinclair wasn't the only one to play that game, he did rather have form in that area!
Re: "crowdfunding before crowdfunding existed"
"Although Sinclair wasn't the only one to play that game, he did rather have form in that area!"
On the other side of the world, the machines came in at something over 8 times the UK price (A BBC micro was something like 2 months of my father's salary as a senior primary school teacher, so understandably, we never got one - even if you had a ZX81 you were well off or a computing fanatic)
But at least you could buy them. It was illegal to sell/bill for products you didn't have in stock
Re: "crowdfunding before crowdfunding existed"
I never received anything from Sinclair without the threat of legal action... one always wondered how much development they were doing with the cash from the orders.
Thanks!
Thanks for the nostalgia hit!
Mine came with the 'Learning Lab', a rather thick book and bunch of cassette tapes.
Seem to remember that Memotech did a rather nice range of modules for it.
Also remember hand entering the code for FIG-Forth; a fun language which used reverse polish notation.
Also it made a rather effective radio jammer!
Sharing a tape recorder with my sister. I used to load and save programs on it and she would record top of the pops over the them, happy days!
The ZX81 was genuinely my first own computer, bought with the earning from a holiday job when I was 16. It kept me occupied until I bought a Spectrum at Uni. Mine is long gone now but I acquired one a couple of years back that a friend of a friend was throwing out.
The edge interfaces on both machines were vey useful, with assistance from a couple of hardware guys I had quite a few peripherals including a 4 fire button fully programmable* joystick for playing Halls of the Things on the Speccie.
*Programmable by attaching crocodile clips to a custom PCB.
I never had a ZX81 - at the time I was going from Commodore PET to a VIC20, but I did go on a school French exchange where the family I was staying with had one. I remember spending what seemed the best part of a day typing in the code for "that program" that had the tyrannosaurus rex advancing menacingly from a 3D maze (without the benefit of the muscle-memory ZX81 owners developed for which keys corresponded to which BASIC commands) only to have it totally crash when I tried to run it. No idea why I didn't save it first, I think I was just used to the Commodores where the worst you'd get if something was wrong with a BASIC program was a ?SYNTAX ERROR IN 270
Computers vs girls
My ZX81 came from WH Smiths back in 81/82. After the ZX81 came an Oric Atmos, it was a revalation to have a proper keyboard. At school we had BBC Acorn and a bit later IBM PC. Then I kinda lost interest for a good few years. Computers could not compete with girls, late teenage years, what do you expect.
Re: Computers vs girls
The girls might have been more interesting but the computers were far easier to get your hands on (and to understand, for that matter)
My ZX81 self-build kit was a present from my parents when I was 14.
It had been packed in such a way that the pins of a couple of the ICs had punched through the membrane keyboard, rendering it useless - it took weeks, and many irate phone calls by my mother, to get a replacement.
Eventually it did all work though, and I spent many a happy/frustrated hour tinkering - I built it into an old Linotype Paul case with a full size keyboard, inverted video output (white text on black background) and a ram expansion on a ribbon cable (so no wobble).
40 years later and I'm still a serial tinkerer and coder.
A few years ago a school friend got me an autograph from Sir Clive with an apology for the damaged keyboard!
I still have a working one, it has a converted to digital output in place of the tuner. I also have an excellent emulation on iPad, by a Kevin Palser..
The ZX81 was life changing for me, no exaggeration. I can still remember the feeling of seeing the thing work for the first time. It was special to be around when this movement was born and took off.
Still got one in the loft
Although it's in a "proper" (well sort of, rather clunky) full size keyboard case, we got sick of the membrane very early on. Plus the case makes the (non Sinclair) RAM pack much less likely to wobble.
Chess in 1K of RAM, 3D Monster Maze, Catacombs, etc etc. Even had a Dig Dug in Hi Res by the time it got updated (to an Acorn Electron). No idea how someone managed to get that to work. I remember it being a swine to load from the tape though.
Re: Still got one in the loft
Nerd attack!
To output graphics the ZX80 and ZX81 rely on the Z80 — it jumps to video memory and attempts to execute. The video logic (discrete or ULA, respectively) spots that based on the high bit of the address and from then on it pushes whatever opcode the CPU was going to fetch into a latch and forces a NOP to the CPU. It's a Z80 so it follows up the opcode fetch with a DRAM refresh cycle, during which the video logic forces the just fetched opcode plus a three-bit-counter on top of the low 9 bits of the refresh address and uses whatever comes back on the bus as the next 8 pixels of video output.
The internal RAM is static, so there's no actual refresh.
(and I've simplified that description a little by omitting HALT; there is some intelligence in there so that if the CPU reads a HALT then it actually gets a HALT, which is how the 1kb machines don't have to maintain a full 32x24 text buffer unless the user has actually filled the display with characters)
So, the two main options for high-res output are:
(1) find a suitable set of locations in ROM to cover a decent number of the possible range of pixel patterns, and use that as your target for the refresh cycles — on a Z80 you can set the top 9 bits of a refresh address, as DRAMs at the time had 7-bit address buses and therefore the Z80 increments across only the low 7 bits. This is how any high-resolution game you played that had odd graphics that weirdly gained or lost lumps as they moved worked.
(2) move the refresh address into RAM. Technically relies on a quirk of the bus, but works with the internal 1kb of RAM and with many expansion packs. But not all. And it's hard to get that much into the internal 1kb. So this approach is better in terms of fidelity, worse in terms of compatibility.
Source: I wrote an emulator, of the attempts-to-be-entirely-accurate variety.
Still got one somewhere
I bought one, used it twice, gave up.
Getting it to talk to the TV was hit and miss (mainly miss), connecting to the tape recorder never worked, and the fake button keyboard membrane was a POS
Absolute waste of money
Its in my spare parts bin, I guess a museum will get it one day
Re: Still got one somewhere
But, but, but... Getting everything working sweetly despite the flaws was the whole point, wasn't it?
Avoid if at all possible...
...tapping in code from this month's magazine. Always wait for next month when the inevitable correction to the code is published.
Although troubleshooting those typos became laid the foundation for the career I have today, so I cannot complain too much. Cheers!
Re: Avoid if at all possible...
Why just wait for the errata in next week's [1]Input when far more fun* was to be had looking at the listings for the other computers and porting the fix over to yours?
* I think that's the word.
[1] https://archive.org/details/inputmagazine
Ha, latecomers
I built a MK14 (look it up), it made the ZX80 look positively palatial in terms of resources.
Re: Ha, latecomers
If you got a MK14 with the trimmings (cassette interface, memory upgrade, TV output), didn't you end up with something not too far away from a ZX80?
Re: Ha, latecomers
Well, other than the fact that the max on board RAM was (IIRC) 384 BYTES, and the terrible INS8060 CPU had no stack pointer and could only handle 4K of RAM at one go without paging ...
Ah, the memories. The ZX-81 was also my first encounter with a computer, my grandfather bought one soon after they first came out. He was a former codebreaker for the Admiralty during WW2, and university professor at Manchester where they had a machine he described as being as large as a room. I still feel particularly sad that he never got to see how modern computing turned out, as he died in 1987.
The one thing that sticks in my mind with the ZX-81 was typing in and running the code for something called "Life", which generated some really interesting (blocky) patterns that evolved over time. It left a huge impression on me, and helped make me into the geek I am today!
I loved my ZX81!
I still have mine and all it's accessories, including the Cassette tape player, haha!
40 YEARS OLD?!?!?
40 YEARS OLD?!?!? How did that happen!! I had one when I was ~10 in 1981. I remember it being connected to an old B & W TV! Also I'm fairly certain it was a 'Timex-Sinclair ZX-81. My how time flies by...
Surprisingly, the company I worked for at the time used a ZX80 in a production environment.
It was used to send messages between floors where the manufacturing plant delivered product to the filling area below. And it was in service for most of the 80s and into the 90s.