The Electron's Operating System, like its big brother the BBC Micro, is capable of managing up to 16 sideways ROMs. These ROMs can contain a variety of software such as word processors, games, languages, tools and utilities.

Acorn Plus 1 or AP1 owners will be familiar with this facility as two sockets are provided beneath the spring-loaded flaps on top of the expansion unit for ROM cartridges.

These are fine, but what about the other 14 sockets? Where are they and can we use them? Unfortunately Acorn haven't provided space for more than two ROMs to be plugged in at once!

The BBC had the very same problem when it came out. It was solved by the addition of ROM boards, either internal or external, which provided space for the extra ROMs.

Now Slogger has produced the Rombox for the Electron. This enables owners to plug in up to eight additional ROMs. It allows firmware (software in ROM) written specifically for the Electron, and some BBC ROMs, to be used.

The unit is constructed of fairly tough plastic, not quite the same creamy colour as the Electron. It's the same height and width, but only one third as deep.

Installation is a piece of cake. It simply plugs into the back of the Electron in the same way as the Acorn Plus 1. Two plastic screws are provided to secure it firmly.

If you already have a Acorn Plus 1 and/or Acorn Plus 3, there's no need to worry. The expansion bus is continued at the back of the Rombox for them to plug into. The unit is compatible with both expansion units and I've had no trouble with either.

In fact the only problem is that with the Rombox, Acorn Plus 3 and Acorn Plus 1, the Electron is nearly one and a half feet deep. Those stories about it getting so big it's falling off the back of the desk are true!

As I said earlier, the operating system can manage up to 16 ROMs, which it numbers 0-15. But not all these ace available to the user, as some are already taken up.

BASIC occupies 10 and 11, and the keyboard, strangely, is treated as sideways ROMs 8 and 9. The Acorn Plus 1's Operating System is 12, and the ROM cartridge sockets are 0 and 1. The ADFS in the Acorn Plus 3 is number 4. So what does this leave?

With both Acorn Plus 1 and Acorn Plus 3 attached, there is room for eight more ROMs - exactly the number of places available on the Rombox.

However it's not that simple. The ROMs are in two banks of four. The left four are fixed as ROMs 4-7. So if you have a Acorn Plus 3 then the first ROM position, 4, is unavailable, although 5, 6 and 7 are OK.

The right bank of four can be set as 0-3 or 12-15. As 0 and 1 are for ROM cartridges it seemed best to have them set up as 12-15. This left 13, 14 and 15 free, as 12 is the Acorn Plus 1.

So, with an unexpanded Electron all eight ROM positions are available. But with both Acorn Plus 1 and Acorn Plus 3, only six are free.

I have three ROMs in use at present - Vine Micros' Addcomm and Slogger's own Starmon and Elkman. All work perfectly with no apparent bugs or hiccups.

It's surprising just how many ROMs are available now for the Electron. You could easily fill all the sockets.

An added bonus with the Rombox is the option to use the rightmost ROM position as a sideways RAM socket.

The extra RAM available would not increase the amount of memory available for running programs, but it would allow data to be stored there.

It would even be possible to save ROMs to disc and load them into the sideways RAM as and when needed, thus freeing ROM sockets.

Slogger has produced a valuable piece of hardware which enables the Electron to use its ability to access Sideways ROMs to the full.

The Rombox fits in nicely with the Acorn Plus 1 and Acorn Plus 3, or can be used on its own.

My only criticism is that the ROMs are rather exposed. I would have preferred them to be under some sort of cover, but this is a minor point and I can't really find fault with its operation.

John King