OLD-COMPUTERS.COM : The Museum

After the success of his two previous computers, the ZX-80 and particularly the ZX-81, in April 1982 Sir Clive Sinclair presents the ZX-Spectrum. For the first time, a computer with high-resolution graphics, colors, sound and 48k RAM was sold under 25£. Once more Sinclair revolutionized the microcomputer industry with new standards.

After the launch of the Spectrum, many other microcomputer manufacturers were forced to reduce their prices, and 17 months after the release of the Spectrum, the sales already reached 1 million units !

The critics first saw the ZX Spectrum as an enhancement of the ZX-81, but it is much more !

The keyboard is very special: rubber keys with a load of colorful inscriptions on them. I even think that the ZX owns the-number-of-inscriptions-on-one-key world record: up to six ! The "3" key for example, is also used for the Basic statement LINE, the TRUE VIDEO mode, the MAGENTA color, the "#" sign and a semi-graphic symbol ! Impressive isn't it?

Impressive, but not very practical. Ok, you can't make typing errors, but it's soooo slow... Anyway, since then many manufacturers adopted this type of keys.

The Sinclair Basic is special and all the statements are entered word by word using the inscriptions on the keys. There is absolutely no way to type those statements letter by letter, just like with the ZX-81.

The screen is divided in two parts : 22 lines used to display the program listing and 2 lines at the bottom to enter the statements... quite unusual, except for Sinclair fans. As you enter the Basic statements each new line is analysed and if there's an error, the ZX prompts you to correct it.

There is a degree of compatibility between the ZX-81 and the ZX-Spectrum Basics as the ZX-81 Basic is a sub-set of the Spectrum's one.

The best feature of the Spectrum is its graphic possibilities. With 256 x 192 pixels, it was one of the highest resolutions for a microcomputer of its range in 1982. LINE and CIRCLE statements are available, as well as 21 semi-graphic symbols and user-definable characters. But unfortunately, colors are limited to 8 x 8 pixels areas, that is to say that you can only specify 1 ink color and 1 paper color per 8 x 8 pixels squares. This is very important to understand the look and feel of most of the Speccy games !

But the greatest drawback is the sound possibilities. There's only a poor beeper controlled by the BEEP statement...
However, in assembly one could do digitized sound, and some guy even wrote a demo which produced four channel sound on that shitty beeper. Of course it wasn't real 4 channel, but it satisfied ears.

The ZX-Spectrum is based upon the classic Z80A microprocessor, a quicker version of the Z-80.

The tape transmission is very reliable (hello Oric) with a transmission rate of 1500 bauds.

A lot of hardware has been developed for the ZX-Spectrum. You could find almost anything you wanted for your Speccy. The most innovative extension was maybe the Sinclair Microdrives which were small mass-storage device using tiny cartridges with endless magnetic tapes. Each cartridge can store about 85k. This is not fantastic, but it was a good and cheap alternative to far more expensive disk drives. These microdrives, slightly modified, were later used with the Sinclair QL.

The Spectrum was surely the most cloned microcomputer in the world ! Apart from the official clones like the Timex 2048 & 2068 sold in the USA, there have been many illegal compatible systems sold especially in the Far East, the old communist area as we say.

In 1984 the Spectrum is replaced by the Spectrum + which is only a Spectrum with a new look: the rainbow is smaller and the design is more "squarish". Underneath you can find two small "feet" to tilt the keyboard just like the brand new PCs ! The keyboard has also changed, it looks like a typewriter-style keyboard but it's not a real one, the striking is really too soft. Some models of the Spectrum+ had a probem whereby when you tipped the machine upside down, some of the keys would fall out! Well I love those strange keyboards they produced to save some money, too cool.

Ok, here is the bottom line: the Spectrum is amazing because it really sold millions in Europe and around the world. Then loads of software was produced along with many peripherals, especially the Sinclair extensions which were quite beautiful with the same design as the ZX. The Spectrum lived long (it is still alive for many) through its several new models : 128, +2 and +3. The programmers have always pushed the Spectrum beyond its limits and produced fantastic games with a computer which was in fact limited.


		+ amazing software library + its design + graphic possibilities + its success + its price				- The rubber keyboard - Poor sound

Adriaan Bloem reports to us:
Yes, there were three different models of the ZX Spectrum. The original ZX Spectrum was referred to as the "Issue 1". They redesigned the system board (optimised it for production), which became the "Issue 2". The last Spectrums were produced in Taiwan, and for this production line the design was once again updated which became "Issue 3".

Officially, the three issues of the machine are the exact same, but because many rather undocumented features were used in ZX Spectrum programs, small differences in timing did show up. For example, the Spectrum put a picture on the TV screen in "underscan" (as opposed to the "overscan" used by DVD players) so there was a border around the screen. It was possible to assign a colour to the border. Quickly changing the colour of the border produced an effect of moving bands in the edge of the screen, an effect which was used when loading programs from tape to show progress. With some nifty timing, the border could also be given two or three large segments of different colours. This timing was different for the different issues though, and I remember asking users the question "What issue is your Spectrum?" at the beginning of some of the games I programmed.

Staffan V. adds:
If I remember correctly the first issue had problems with the ULA (Uncommitted Logic Array, basically the input/output chip) so that INKEY$ (gives the currently pressed key) only worked in 50% of the cases. This was solved by adding a small PCB board (called "dead cockroach") piggyback on the ULA. In issue 2 there still were some problems with the ULA, but it was fixed by adding a transistor (I think) on top of the ULA. Issue 3 had no ULA problems.

Dave Cridland, about the keyboard :
The picture you have there is a 48k - the 16k not only had less memory (although you could upgrade), but also had a lighter shade of grey for the infamous rubber keys. The "Issue 1" Spectrums were, I think, all 16k, and even after upgrading them to 48k, they weren't quite compatible with the later models, and thus the later games. The Issue 1 was also shipped drastically late - they were mostly sold mail order, so anyone who'd ordered - and therefore paid - for one was compensated by getting a free ZX Printer with vast numbers of rolls of the "shiny toilet paper" that this noisy thermal printer used.

Upgrade kit by Ali Mclaren:
After introduction of the ZX Spectrum + an upgrade kit was made available for owners of the bog standard Spectrum. As I recall the kit included the new shell (with proper hard keys) and a reset button. The connections for this had to be soldered (!) into place on the mother board. I have a sneaking suspicion that there was an extra memory chip to upgrade from 24k to 48K but I'm not as sure about that.

Better display, by Mark Slabbert:
At times the colour display "drifted" causing a slight blurring of the tv image. Beside returning the tv you could easily open the casing and adjust either a variable capacitor or resistor (can not remember which) to stabilise the image and sharpen the display. Worked like a charm.
Despite the strange keys the lettering never seemed to come off even after years of typing. Wish some of my modern remotes were of the same quality.

Grant MacDonald adds:
There were also many official and un-official external memory modules to increase the memory to the full 48K. Many of these had heat problems and would get quite hot! They also suffered from intermittant connections and I remember many times waiting for my friends Speccy to load from tape and to start running a game JUST for us to get a bit over eager on the first key-strokes causing the ram-pack to wobble and the game to crash.

Later games used modified code to compress the tones used on the tape drive and "turbo load" games or use techniques called "headerless" loading (normal Speccy files had a short header on the tape containing information about what was to follow, how big it was, and where in RAM to locate it) these turbo loaders could be more sensitive to the tape deck used and manufacturers created modified tape deck where the normal screw used to adjust the angle of the tape head was replaced by a knob to make getting the exact angle of tape/head easier.

António Vasconcelos disagrees:
It's a error to think that typing was slow on a rubber-keyed Spectrum. *After* you mastered the keyboard (witch would take same time) you would be able to write BASIC programs much faster than anyone could with a standard keyboard. I had to type a few programs I wrote on the Spectrum into an Amstrad PCW for printing purposes, and I know it took me much longer that what it took me to write the original program.