“straw and clay” computers that dropped PC prices

In 1977, the PC market was dominated by the Big Three: the Apple II, the Commodore PET, and the TRS-80. Their prices were $1298, $795 and $600 respectively. And at that time they were not at all publicly available.

In 1979 Texas Instruments TI99/4 and Atari 400 appeared (about $550). These models were cheaper, and besides, they offered good graphics and sound.
Not just a computer, but something that made it possible to play.

But in 1980, a strange “craft” from Science of Cambridge in the UK came out, the appearance of which led to a significant decrease in the price of home PCs.

This is the Sinclair ZX80. Its development had only one goal: to make everything as cheap as possible.

Advertising ZX80

For the sake of fairness, I note that the first was still the Mk14 (from the same Science of Cambridge Ltd) for 39.5 pounds, but I can’t call it a computer (256 bytes of RAM, without a power supply and a case included).

The ZX80 DIY kit was offered for £79, while the finished computer sold for just £100 ($140).

This machine was designed for the UK and outputs video in PAL standard (export models were shipped to the US with NTSC support).


How did you manage to achieve such cheapness? Despite the fact that at first glance, this thing looks pretty nice, everything is known in detail. But we must pay tribute: the simplicity of this machine is amazing!


Two halves of thin plastic. The size of the computer is smaller than an A4 sheet (and the less plastic, the cheaper).

Did you notice the cutouts of the cooling system in the first picture? She is not there. It’s just drawn.

Inside – a screen from interference. In fact, this is just a metal coating on plastic.

All computer ports are located on the back. Except for the antenna output, everything is the same! One for 9V power supply, and two for the tape recorder. If mixed up, it is quite possible to burn the machine.

Rear panel of the ZX80

If you look closely at the photo above, you can see the plastic latches on which the two halves of the case are attached. Pa-bam! You will not find screws there.

There is no power switch on the case. Even here we decided to save money.


ZX80 topless

  1. The keyboard is located on the printed circuit board. Film.
  2. The heart of the computer is the Z80 clocked at 3.25 MHz (some had a cheaper counterpart from NEC).
  3. ROM 4KB – BASIC, character generator, I / O procedures and more.
  4. RAM 1KB (expandable).
  5. Everything else is standard TTL.

Where are the audio and video processors? And they are not. The computer doesn’t even have a tweeter, although when connected to a TV you will hear a terrible rattle. It is treated only by reducing the volume.

Video output is handled by the processor. 8 pixels each, after which – again waiting for the next piece of data.

Incidentally, the 3.25 MHz processor frequency was probably chosen to help the processor synchronize with the composite display.

In fact, this system is so cheap that it uses a ceramic resonator instead of a crystal oscillator.

Also pay attention to the board: there is a feeling that its wiring was done manually.



In the comments on my previous posts, some were nostalgic about the Speccy keyboard: they say, how convenient, I pressed it – and immediately a whole team was on the screen. I swore at her after switching to PC. For a normal person who quickly types on the keyboard, clamping all these registers and looking for the right button with the command on the stickers is a living hell.

User guide

But even more terrifying is that the computer can either display something on the screen or receive commands from you. That is, while typing the program, the screen constantly goes out and lights up. This is a consequence of the fact that the computer does not have a video chip.

There is another amazing feature. You always type commands at the bottom of the screen. As soon as you finish a line, the ZX80 will send it to the top.

And that’s why. If you type this program:

20 GOTO 10

Then the screen will not scroll, and the program will end with an error (which are displayed in the form of codes, not words – to save memory) “there is no more space on the screen.”

The processor cannot display the screen while the program is running.

But that’s not all. The computer has only text mode. The screen is 32 characters wide and 24 characters high.

Set of signs and commands ZX80

Not so bad by 1980 standards, right? But this is as much as 768 bytes of RAM. From 1024.

That is, only 256 bytes remain for the code. In fact, the operating system uses another part of this memory for its own purposes.

What can be put in there? And here the thoughtfulness of this simple machine affects. As soon as you use more than 256 bytes, the program starts to take up screen memory. And then the screen starts to “shrink” from the bottom up.

The only way to store ZX80 programs was to connect a cassette recorder, which was the standard solution for home computers of the time. And other media never appeared, although there was a cartridge slot.

Unlike consoles, it has never been used for gaming. By the way, the connector for the cartridge is “dad”. Why do you think? Probably the “daddy” is cheaper (remember, all cartridges for set-top boxes were with this connector?).


There were several clones of the Space Invaders, Kong and Pacman games. This game is remarkable in that it was possible to make them at all.

Space Invaders

Donkey Kong


It’s amazing that games are able to switch from gameplay to video display.

So the ZX80 is a terrible computer from a user’s point of view, designed with one goal in mind: to be cheap.

However, it was commercially successful (sold over 50,000 copies).

“Second coming”

Already in the next 1981, a new model called the ZX81 was introduced.

Kit with 16K cartridge and printer

This computer model was more popular. And even smaller.

It had virtually the same membrane keyboard as the ZX80, and the back has the same expansion port.

There are also differences:

  • It uses real metal screws.
  • There are only a few chips on the motherboard: the same Z80, 8K ROM, 1K RAM and ULA to reduce the cost.

ZX81 internals

The main changes affected BASIC. The original BASIC could only handle integers, while the new BASIC could handle floating point. There were also commands for drawing primitive graphics.

And there was also a SLOW mode. It allowed you to generate video and simultaneously execute program code. In this mode, the processor becomes multitasking and spends about 70% of its time drawing the screen, and the rest of the time is busy with everything else.

Anyway, no flicker.

Sinclair also offered a way for ZX80 owners to upgrade to the ZX81. It was possible to replace the chip, and upgrade the keyboard with stickers with additional features. Only 20% of the cost of the ZX81. A fair deal.

Interestingly, the ZX81 had a bigger impact on the US home PC market (Timex Sinclair 1000 already with 2K on board).

Timex also sold a 16K RAM module and a tiny Timex personal printer (Sinclair had a similar one).

There were also several applications on cassettes that were sold in stores along with the PC. Some were marked “16K”.

It is noteworthy that enthusiasts still found ways to get sound from a computer, using a tape recorder port to generate simple audio signals.

The Timex 1000 went up to $49.

There was one funny situation that Commodore created. Conducting an advertising campaign, the manufacturer provided a $100 discount when exchanging for any computer or gaming system. That is, you could buy a Timex 1000 for $50 and exchange it for a Commodore at a discount.

A couple of years later, Timex introduced the Sinclair 1500 with 16K RAM and an improved keyboard.
It failed in the market due to tougher competition by 1983 (then the Commodore VIC-20 and Sinclair ZX Spectrum had already appeared).

The beginning of the 80s was rich in ups and downs in the computer industry. In the same 1980, the Apple III appeared, which was withdrawn from sales a couple of years later. Or a desktop portable IBM 5120 worth $13,500. A year later, the IBM PC was released. He managed to come out on top in terms of sales, leaving behind the products of Apple and many other manufacturers.

Despite their ugliness and limitations, the ZX80/81 played a significant role in finding ways to reduce the cost of home PCs, and in the appearance of the beloved by many ZX Spectrum, Commodore C64, Amstrad CPC, which became available to ordinary users.

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