The ZX Interface 2 was a hardware peripheral by the manufacturers of the ZX Spectrum, Sinclair Research.

Designed as and add-on for their popular home computer (the ZX Spectrum and not the ZX81 or ZX80) it was released in September of 1983.

It had a pretty nifty two joystick ports and a ROM cartridge slot, which offered instantaneous data loading times.

The joystick ports were not compatible with the most popular joystick type on the Spectrum which was the Kempston interface. This was an immediate downside as existing games released prior to the interface 2 did not work with it.

From this point on it must be noted that most Spectrum games released post Interface 2 launch were compatible with it (as well as the likes of Kempston, Protek et al).

The interface 2 therefore allowed you to connect two joysticks to your machine as well as having a ROM cartridge plugged in. In addition to this the pass-through expansion bus provided allowed a ZX Printer to be attached - but nothing else.

The ROM cartridges provided an alternative method of data storage - with cassettes being the most common choice at the time.

Unfortunately the ROM carts were very expensive (for example a game on ROM could cost in the region of £14.95 which was very expensive for the era.)

Consequently availability of cartridge software was very limited: With the cost being roughly twice as much as the same game on cassette, coupled with the fact that each cartridge could only hold 16KB of data, made the technology almost immediately obsolete as the majority of customers opted to purchase the 48K ZX Spectrum - the 16K model was short lived.

Software house Ultimate Play the game were one company who embraced the ROM cartridge but moved to 48K development only after they released Jetpac.

Only ten games were commercially released on ROM cartridge which were:

1. Jetpac - by Ultimate play the game
2. Pssst - by Ultimate play the game
3. Cookie - by Ultimate play the game
4. Tranz Am - by Ultimate play the game
5. Chess - by Psion / Sinclair
6. Backgammon - by Psion / Sinclair
7. Hungry Horace - by Sinclair
8. Horace and the Spiders - by Sinclair
9. Planetoids - by Sinclair
10. Space Raiders - by Sinclair

For those that had them, ROM cartridges were great. All you did was plug the cart into the slot on the Interface 2 and voila - the game was loaded instantly! I suppose you could call it plug and play! Not only that but they were more robust than standard cassettes which were of course prone to twisting or even being chewed by your tape deck. No such hassles with ROM cartridges.

If the ROM cartridges had been manufactured to hold 48KB of data then the story could have been different. More games would have been available on this format and eventually the price of them may well have fallen.

Due to the 16K limitation ROM cartridge games for the ZX Spectrum are now very rare and have become collectors items. Grab one if you can.

The interface 2 came with two joystick ports that (unlike the Kempston interface) were mapped to actual key presses.

Player 1 was mapped to number keys 1 to 5 and player 2 was mapped to number keys 6 to 0.

This initially seemed at odds with Sinclair's own keyboard layout, given that the keyboard itself had the cursor keys mapped from 5 to 8 with the 0 key typically being used by games as a 'fire button'.

Joystick interfaces that mapped to the cursor keys were available to buy, but like the most popular Kempston interface they were limited to only supporting a single joystick. This 'twin joystick' feature of the ZX Interface 2 ensured it became a popular add-on for gamers. Having the option for two players to both play a game with a joystick each was excellent.

One game that was excellent for two players was 1985's 'The Way of the Exploding Fist' - a brilliant beat em up game from Melbourne House.

With each player having 18 karate moves in total that they could perform, a lot of players preferred to use a joystick to do so rather than the keyboard. Using the eight directions of the joystick for movement, blocking and punching and using the fire-button to execute kicking and sweeping moves made controlling your fighter relatively easy.

Having both players with the option to play with joysticks was one of the occasions that the Sinclair Interface 2 really came into it's own.

Match Day was released in 1984 by Ocean Software. It was probably the first proper 'football' game on a home computer. Previous football games (or soccer games) had usually been variants on the 'bat and ball' theme.

Match Day actually had proper 'player' and implemented the rules of the sport. Playing against a friend was where the game really came into it's own - and once again the Sinclair Interface 2 came out on top here. Rather than having to make do with the keyboard, both players could use the joystick to make those all important tackles and execute those long range shots. Quality stuff.

Match day was so popular that a sequel was developed a couple of years later, the even better Match Day II. Once again the most fun was to had playing against a friend, and once again both players using the joystick made for the best matches.

Thanks Interface 2!