First Computer At Home
The Sinclair ZX Spectrum is a particularly significant 8-bit computer for me, because it was the first computer that I ever owned.
Improving on the ZX81
Like the ZX81 before it, the ZX Spectrum was heavily advertised in various magazines that I read back in the 80s. Released in 1982, the Spectrum improved on the ZX81 in a number of ways, such as adding colour and sound, as well as more memory (16 / 48 KB, instead of 1 KB), and an improved keyboard. It also had a bigger ROM — at 16 KB it was twice as big as the one in the ZX81.
The Spectrum’s Z80 microprocessor was clocked a little faster than in the ZX81 (3.5 MHz instead of 3.25 MHz), and it did away with its predecessor’s FAST and SLOW modes, by delivering the best of both modes.
The Spectrum’s rubber keyboard wasn’t anything like as good as the one found on machines like the Apple II and BBC Micro. Some people think the Oric-1 had a better keyboard. Whether that’s true or not, it was certainly a big improvement over the membrane keyboard found on the ZX81.
Programs were usually stored on cassette, using a normal audio cassette recorder. Running at 1500 bps, the Spectrum’s cassette interface was about five times faster than the ZX81’s. As an alternative to cassette, the optional Microdrive could be used instead. Microdrives were a cheap but unreliable floppy disk alternative, also used later on the Sinclair QL.
Despite its improvements over the ZX81, the Spectrum was still a small and relatively simple machine, positioned firmly at the cheaper end of the market. It had very few external connections. The single expansion port allowed things like the ZX Printer (see later) to be added, as well as Sinclair’s Interface 1 and 2, plus various third-party peripherals. These enabled the Spectrum to connect to things like joysticks, Microdrives, modems and serial printers.
Becoming a ZX Spectrum Owner
My high school computer studies class got me interested in computing in the early 80s. But the Apple II and BBC Micro which we used in class were quite expensive, and few parents could afford to buy one for their children. So when my computer studies teacher said she had a Sinclair ZX81 for sale, I was interested. Unfortunately, by the time I’d convinced my parents, a classmate had beat me to it.
A few months after missing out on the ZX81, my parents bought me a 16K Sinclair ZX Spectrum as a Christmas present! I was very excited, and soon forgot about the ZX81. I’ll never forget loading the Horizons cassette for the first time, and playing games such as Night Flite and Horace Goes Skiing.
Wanting to Program
The idea of owning a programmable computer with a built-in sound generator was very appealing to me as a child. The Spectrum’s shortcomings didn’t matter too much back then. The Spectrum was mine, and I was just glad to have anything which I could use at home.
As the months went by, I explored every aspect of the Spectrum, and read all the manuals. I learned to program using the Spectrum’s version of BASIC, as well as ‘machine code’ (Z80 assembly language).
The Spectrum’s BASIC language had support for graphics and sound, unlike machines such as the Commodore 64. That made it easy for beginners to experiment.
Considering its reasonable price, the Spectrum’s graphics were not bad at 256 x 192 with 8 colours (or 15 including ‘bright’ versions). But its colour attribute system limited each 8 x 8 block to just two different colours.
I tried to make music and percussion sounds, by writing my own software. But after a while, I became increasingly disappointed with the Spectrum’s sound facilities. Rather like the Apple II, the Spectrum could only generate sound as a series of pulses or clicks, which used processor time. So there was no proper control over waveform or volume — and there was only a single channel.
The Spectrum’s BASIC manual had a silly comment in the chapter on sound, saying that it could only play one note at a time, because it only had one loudspeaker. Even as a child, I knew this was nonsense!
Software tricks could go some way to making more complex sounds, but the lack of a dedicated sound generator chip (such as that found in the BBC Micro or Oric-1) meant that it was not the best choice for someone who was interested in making music.
I was interested in electronics from an early age, having previously experimented with various circuits and audio amplifiers. So when I was frustrated by the inferior sound generator, at 14–15 years old I designed and built a circuit to connect an external sound generator chip, which I’d spotted in the Maplin catalogue. I was pleased when my sound generator add-on worked as expected, and I used it for weeks. But then disaster struck…
There wasn’t enough room at home to leave the Spectrum set up permanently, so I used to store it away every night. That meant that the polarising key on the edge connector — which connected my sound circuit to the Spectrum’s expansion port — soon wore out. It then shorted out the contacts on the Spectrum’s PCB, which damaged the ULA chip in the computer. I complained to Maplin, and they gave me a free replacement connector.
After the Spectrum was repaired, I couldn’t afford to risk damaging it again, and stopped experimenting with add-ons.
New Models — Too Late
In 1984, the Spectrum+ was released. That was really just a 48K machine with a different case and keyboard — and it still lacked a dedicated sound generator chip. It seemed like the Spectrum was never going to get any improvements in that area, so I started looking at computers which had good sound facilities.
The Commodore 64 grabbed my attention. Its SID chip, which was responsible for sound, seemed like a sort of mini-synthesizer — so it wasn’t long before I switched to that machine. (But that’s another story…)
In 1986, it was a little frustrating to see Amstrad take over the Spectrum and the Sinclair brand, especially when they released new and improved models — starting with the ZX Spectrum +2.
In addition to an integrated cassette recorder, the Spectrum +2 had more RAM. It also had — at long last — a sound generator chip! If it had arrived sooner, I may have stayed with the Spectrum — although the Commodore 64’s SID chip was still more sophisticated.
The Smell of the ZX Printer
Towards the end of my time with the Spectrum, my parents bought me a ZX Printer as a birthday present. It was very nice to have, but I was a little disappointed that it could not print on ordinary paper, and that it was so small.
The ZX Printer required its own special rolls of aluminium-coated paper — and they were expensive, especially considering how small they were! It was a novelty to print screen-shots and program listings. I remember attaching a program listing to a school project, and feeling slightly embarrassed about it being on narrow, curled-up, silver-coloured paper. Ultimately, the printer was of limited practical use.
When using the ZX Printer, in the back of my mind, I always wondered whether the smell of burning aluminium which it produced was harmful!
Around the time I had a ZX Printer, I seem to remember Oric computers having a small printer which could print in four colours, on narrow rolls of normal paper. The Oric’s better printer and sound certainly made me a little envious.
Sadly, my original 16K Spectrum had to be sold in the 1980s, to help pay for my next computer, the Commodore 64. But around 1988, I bought a second hand 48K ZX Spectrum, which I still have.
Unfortunately, my replacement Spectrum wasn’t in very good condition when I bought it. That’s a shame, because my original 16K model was in mint condition.
From time to time, I set up my ZX Spectrum again. Those old cassettes bring back plenty of memories. And I can still remember some BASIC demo programs — as well as some Z80 instructions, such as DJNZ!
Do you have memories of using the ZX Spectrum?
Share your thoughts in the comments section below.