The ZX81 was my first computer, and it certainly had a massive impact on the 6 year old me. I am sure I don't need to tell you all, but if you want to see why the ZX81 was so important, you can build a ZX81 compatible kit from basic logic chips. www.tindie.com/products/tyn...

45 years old today. Did the ZX81 change your life? en.wikipedia.org/wiki/ZX81

From one issue of a US mag for the ZX81..

Fun fact: The ZX Spectrum's rubber keys were originally going to be hard plastic. Sinclair went with rubber to save 2p per unit. That 2p decision gave an entire generation a typing experience they would complain about for the next 40 years.

Trying to find a new 15volt AC power supply for the TS2068. It’s tricky!

I remember in quite some detail, the nuances of programming the ZX81 in 1981. That’s 45 years ago. I wonder if the kiddies of today will remember the stupid ChatGPT prompts they were using in 2026, in 2071.

The joyous thing about ZX81 BASIC is that the INPUT statement allowed entry of BASIC expressions, eg 10/SIN(77) What a time to be alive!

AVAILABLE NOW: 1K of RAM. That's 1,024 bytes of pure, unbridled possibility. Write a game. Write a calculator. Write half a calculator. The choice is yours.

If you wondered how a #ZX81 could use a 64K RAM pack, this advert lays it out pretty clearly. “With difficulty”.

My multi-cpu assembler, OmniAsm now supports the GB CPU as well as Z80 and 6502!! I still need to tweak the parsing of some opcodes like (FF00+XX) and SP+XX, for example, but I think the rest are working :)

My kind of magazine advert.

The Sinclair ZX80 Manual has all the right characters but not necessarily in the right order. 🙂 CHR$ 228 is “>” CHR$ 229 is “<“

ZX History - March 1980: PCW reviews the ZX80. “The ZX80 appears to be a well thought out machine both in terms of hardware and software.” [...] “I hope Mr Sinclair and his merry men of Cambridge can cope with the flood of (1/2)

ZX History - February 1981: The ZX80!

The ZX81 didn’t have any sound generating hardware (making the TV buzz doesn’t count, nor does abusing the cassette interface). So a box like this was impressive - three channel sound! Including white noise! Yes please!

There's a specific joy in powering on a 44-year-old computer and seeing that inverse K cursor blinking at you. It doesn't want your password. It doesn't need an update. It just wants you to type something. Anything. Go on.

I "expanded" the TI-74 in this issue of Circuit Cellar. I wanted to do something similar with my Sinclair when I got it in 82 but most computer people I knew then were not data acq/control types.

That’s a lot of expansion. Is it maybe too much expansion? I think it might be too much.

Found a picture of it & it doesn't so much look like a keyboard as more just a clear sheet of plastic with some holes in it? From the advert I was imagining a sort of soft plastic sheet with a raised bubble/dome over every key, but it's almost the opposite of that. timexsinclair.com/product/touc...

I swear every other advert in this US magazine for ZX81 users (it’s called SYNC) is for a keyboard. Americans just couldn’t cope with the membrane.

Feels a little threatening to be honest.

Claude is down this morning, so I am powering up the back-up.

The ZX81 manual taught an entire generation of British children to program. It also taught them that "SCROLL" was not a medieval weapon and "POKE" was not rude. Well. Not in that context.

Can’t take a screenshot? Don’t worry - just draw it by hand. Also - funny you don’t hear much about Biorythms anymore.

The GI SP0256 speech synth chip was the easiest way to add “speech” hardware to an 8-bit micro in the early 1980s. Designing the circuit would entail choices such as memory mapped or IO mapped? Dedicated clock or borrow system clock?

Maybe of interest: www.siliconvault.app

Or a foot long. Either is good.

I want a tower at least 60cm tall of computing POWER.

New blog post - The repair of an Acorn A5000 RISC PC where the CMOS battery leaked not once, but twice in the last 30 years. blog.tynemouthsoftware.co.uk/2026/03/acor... Plus a seemingly unrelated hard drive access problem.

FUN FACT on a ZX81: Enter a listing that is just 10 REM with no characters after REM Then POKE 16514,126. Then try the view the listing. Also try with 127, and try to edit the line. Or maybe it's the other way round, but one of these allowed edit to be attempted.

What was the first program you ever typed in from a magazine listing, only to discover you'd made a typo on line 340 and had to spend an hour finding it? I'll go first: it was always line 340.

Things that have more memory than a ZX81: - A goldfish - A greeting card that plays music - The part of your brain that remembers where you left your keys And yet we wrote chess programs for it. Somehow.

In 1982, Sinclair Research was selling so many ZX Spectrums that they ran out of cardboard boxes. The computers were ready. The packaging wasn't. Somewhere in Dundee, thousands of Spectrums sat naked on pallets, waiting to be clothed.

Problem solved.

We've received your complaint about the ZX81 keyboard. We appreciate your feedback. We also appreciate that you managed to type the complaint on it. That must have taken tremendous effort.

Some days I just want to write stupid BASIC programs on an 8 bit computer.

DCP Digitalker Speech Pack on the Sinclair ZX81.

People are concerned that I'm using this technology to draw art that wouldn't fit into the ZX81's extremely limited 1K memory, however it's not a problem, because I've drawn a ram pack.

You have two options in life: you can worry about things you can't control, or you can do the things that you love. I'm choosing the latter, I'm choosing to poorly draw a snail on a fake ZX81 art package.

Don’t let the disparity between the advertising images and actual graphics get to you: Quicksilva’s QS Defender was an amazingly fast and fun game for the little #ZX81.

Easy to install! Hides your entire ZX81! Allows touch typing! Has the company name, address and phone number printed right there!

Are you nerdy enough to know what will happen if you RUN this and why?

The accompanying photo is interesting as that Spectrum never shipped. Instead the US got the TS2068 in silver with a cartridge port.

Back in the March/April 1983 issue of Sync magazine, 43(!) years ago, they report the US market was waiting for the Spectrum.

I'll just nip down to Maplins and .. Oh. Bugger.

Smeg.

Unwrapping the cellophane off a new cassette tape. #GoodFeelings1980s

The last ROM you’ll need? theoasisbbs.com/one-rom-hard...

*Sarah McLachlin music plays* You can help this computer, or you can turn the page.

Did you ever see or use a modem on the #ZX81?