One of the main reasons I enjoyed the recent Micro Men drama so much was that it featured all three computers (other than PCs) which I have owned in my life. And by owned I mean “had access to in my home as a child”. Over the next couple of weeks I’ll be looking back at what, amazingly, was considered cutting edge technology of the time.
The first such machine is the ZX81, Sinclair’s second home machine. Today that gives me a lack of retro kudos because I didn’t have the original ZX80 model. But at the time, it meant I had a better machine than my friend Gavin, and even when you are eight years old, that’s what really matters.
If somebody produced a full-blown computer with the dimensions of a ZX81 today, they’d be lauded as having produced the ultimate netbook: it was roughly the size of a thin hardback book. However, once you compare its powers to that of a modern smartphone, its compactness loses its attractiveness.
Perhaps the best known spec of the ZX81 was that it had 1K of RAM. That’s 1,024 bytes, or a whopping 8,192 bits. That people were able to write any functioning programs given this limitation was impressive. That somebody managed to get the 1K model to play chess was a miracle.
The machine could also be expanded to 16K. However, this was not through today’s thumbnail size memory cards. Instead, users had to plug in a RAM expansion pack, remembering to follow Sir Clive Sinclair’s advice to hold it in place with Blu-Tack. This wasn’t the case in my home however: my dad, a keen electrical engineer, built his own expansion pack which was roughly the size of a shoebox.
Getting sound from the ZX81 was a triumph of creativity over technology. The computer did not have a sound chip or speakers as such. However, as a ZX81 FAQ site reminds me, there were two unofficial ways to bring the noise. The first was to attach it to a cassette recorder or amplifier, which could then be persuaded to emit something resembling a sound. The second was to take advantage of the fact that switching between the machine’s two display modes could produce a noise on the TV set you had to use for your monitor. A carefully written program could thus play what technically counted as a tune.
Another flaw in the ZX81 was that it didn’t come with a fan. It was certainly common behavior to keep the machine cool by placing a glass of iced water on it, though I’ve not been able to confirm my memory that this was official Sinclair advice.
So how on earth did the ZX81 sell a reported 1.5 million units? Well, the mere fact that you could actually program a computer in your own home (and even build one if you bought the kit rather than the assembled version) was an amazing concept in itself. That the machine only cost £69.95 (approximately £218 or $356 in today’s money) was enough to make it a must-have for any self-respecting geek.
And how you could possibly resist a machine that, 28 years later, is listed on Wikipedia with the note “There was a bug present in the original ZX81 ROM that resulted in the square root of 0.25 being calculated as 1.3591409 rather than 0.5.” Sure beats the red ring of death.