It's perhaps symptomatic of the confusion that was the Acorn Electron add-on market that a great deal of arcade games do not incorporate code allowing them to be played with a joystick. When Acorn Computers Ltd first released the Elk, they indicated that there would subsequently be a joystick extension in only a very blase fashion. Indeed, they were hedging their bets, waiting to see if the Elk would take off before splashing out the cash for the production run of the Acorn Plus 1. In the ten months they spent perfecting this "official" upgrade though, a range of third party joystick interfaces appeared on the market.

Power Software's joystick interface for the Electron is one of the rarest, biggest (in size) and under-reviewed products to ever find its way to EUG HQ. It comes in a box about the same size as a domestic VHS cassette which is decorated in colourful fashion with racing cars, an angry looking gorilla, a frog and fighting space cruisers. Displayed prominently are the taglines "High speed ROM software", "Converts virtually all games to joystick", "Just plug in and go!" and "Compatible with all 'Atari-type' 9-pin joysticks".

Opening the box, we find a smooth cream-coloured attachment measuring 15cm x 7cm x 2cm, with a female edge connector on one side and the standard 9-pin joystick connector (the popular format over Atari, Amiga and Commodore 64 machines) on the other. Like the rest of the competition, it plugs onto the expansion port of the totally unexpanded Elk. In doing so, it prevents any other upgrade (disc system, printer port, etc) being installed and leaves the user with only a tape-based machine.

So far then, the interface is identical to those produced by Bud Computers, First Byte and Zip-Stick. However, it has one immediate advantage; the "controlling program" is contained in a ROM chip inside the affixed beige slab, not on a separate cassette, and possibly this is why Power's joystick interface is more elongated than the rest. Packs produced by the other Bud colonies consisted of a square interface and a "conversion cassette". On these, the user must connect the interface, load up the cassette, type in a few commands and then insert the original game cassette and load it in turn. A long process fraught with unexpected difficulties (like issuing the wrong commands or pressing BREAK accidentally) just to be able to play with a joystick when the facility is standard on the majority of other formats!

Happily, the rigmarole of ejecting and inserting more than one tape is unnecessary with Power's extension. On turning on the Elk after it has been attached, the *HELP command gives "Power Joystick Interface" along with the OS number, and the command *JOY enters the control program. Here you must input the keys for left, right, up, down and fire which are used in the game you wish (to use the joystick) to play.

The routine employed therefore is a fairly common one, intercepting the values passed to the interface and redirecting them in such a way that the machine itself believes it is receiving an INKEY value (a key being pressed) and moves accordingly. The first potential problem however is that although INKEY is the most common method of testing for keypresses, it is not always the system employed.

To get around this problem, a "key detection option" has also been included which, the instructions state, may fix a few games where "osbyte &81 is emulated and the X and Y registers instead specify a time limit". Of the games tested with this interface, there were none where using this second method of "key detection" improved an otherwise unresponsive game. Even if it does bestow an advantage on the rare title, the control program would be much improved without it. Why? Because for each of the five keys you must input, you must also choose the method of "key detection" by typing "1" or "2". As it seems you never really need "2", you typically need to type "1","Z","1","X","1","*","1","?","1","RETURN" before loading the game you wish to play. Surely all the "1"'s are unnecessary!

This minor niggle mastered, it's on to testing a number of games that don't include a joystick option to see if the interface really will convert them. As you might expect, the claim to convert virtually all games turns out to be something of an exaggeration [Possibly not at the time of its launch though - Ed] and the more complicated the program, the less the interface measures up to its own hype. Audiogenic's Fab Four compilation (Sphere Of Destiny 2, Thunderstruck 2, Psycastria 2 and Omega Orb) all crashed, behaved strangely or simply ignored the joystick. Similarly, Birdstrike, Star Drifter and Palace Of Magic were also having none of its input.

Fortunately, a comparable number of professional titles did benefit. In addition to almost all Micro Power titles, Orbital, Santa's Delivery, Bouncing Bombs, Kissin' Kousins and Chuckie Egg all benefited considerably from the arcade 'feel' a joystick gives. Quite surprisingly, Mikie (which is almost 100% machine code) also accepted the interface, but unfortunately the extra "Shout" key (which couldn't be defined as the Fire button was already assigned to "Jump") rendered some levels only playable on the keys. Although this is also a potential problem (there being more keys than the four directions and fire button), the keys are not disabled so you can always try a particular title out with the joystick interface and, if too fiddly, revert to using the keys in the middle of play.

On the whole then, this overlooked product isn't bad. The fact that it leaves the user with only a tape-based system smarts a little but, as indicated above, no-one knew for sure whether Acorn's official expansion would ever make it at the time Power's interface was released so this is understandable. (The Acorn Plus 1/AP1 requires a different type of joystick and for all games to be written either using the ADVAL command - or by similar 'assigning' via a control program - so is no less complicated in practice!) Its original price was £24.95: twice that of its third party siblings but less than half of the ultimate official Acorn Plus 1. My own opinion is it was worthy of such a price tag. Its eventual failure was no doubt due to lack of publicity and the mess of the market at the time.

Dave E