You may well be wondering what a ROM board is and why you might need one. To explain, consider the case of the BBC Micro. One of the features that makes this micro stand out from the competition is the ability to plug in special memory chips containing, for example, other programming languages and utility software. These memory devices are in two forms known as ROMs (Read Only Memories) or EPROMs (a reusable form of ROM). Their contents cannot be altered by writing to them, unlike the normal RAM (Random Access Memory) used for your own programs and data in your Electron. The BBC Micro is capable of accessing up to sixteen different ROM devices, but the Electron does not include the necessary hardware for this task. This has prompted several hardware manufacturers to design suitable add-on units to rectify this situation. Sir Computers of Cardiff appear to have won the race to produce the first production-line product.

The Sir add-on ROM pack complete unit consists of two circuit boards enclosed in a case and a manual. The whole unit plugs in to the rear of the Electron and itself has a further identical connector allowing for even more expansion.

The unit is very large - the main circuit board used is slightly larger than the Electron's main circuit board - and is constructed to a very high standard. However, it is a pity that the high quality of the design did not continue on to the edge of this board. Our review board used several small edge connectors, which did not appear to be very strong, in order to connect the two boards that are used together.

We plugged a BBC Micro Graphics ROM into the expansion board, and on connecting the unit to an Electron, switching on, and typing:

*HELP (RETURN)

the following message was displayed:

GRAPHICS EXTENSION 1.03

OS 1.00

This proved that the board was working - at least to the extent of being able to recognise the Graphics ROM. In fact, almost all the commands offered by this ROM worked well on the Electron.

The board was then filled to its capacity of twelve BBC Micro ROMs - there being no available Electron ROMs at present. The Electron's power supply withstood the extra load imposed upon it by this. However, the majority of the software tested failed to operate correctly, if it worked at all. This is in no way due to Sir's add-on unit. In fact, the only ROMs which operated correctly were View and BCPL, both written by Acornsoft. The high failure rate was largely due to the extensive use of Mode 7 which is not available on the Electron. The Acornsoft ROMs are not mode-dependent.

The board offers the user several configurations for ROM and RAM. All the options are link-selectable, i.e. no soldering is required. The first four sockets can be configured to accept any combination of 2K, 4K, 8K or 16K ROM or static RAM devices. The ability to mix devices allows ROM-based software to be fully self-contained with its own RAM workspace, without taking any of the precious user RAM, but any extra RAM added to the board in this way cannot be used to extend the main memory area of the Electron. The rest of the sockets will accept 8K or 16K ROM devices, but can be individually changed to take 2K or 4K devices.

Despite the apparently precarious connection of the ROM board to the Electron, which is somewhat reminiscent of the old ZX81 RAM pack, the computer failed to crash despite repeated attempts on our part to induce failure. We understand from Sir Computers that both boards, in production models, will be enclosed in a single case, the back of which will form a direct image of the rear of the Electron, allowing other peripherals to be added. Our review sample, a pre-production unit, was without a case.

It would not be fair to comment too much on the manual we received since it was a pre-release version, although the text and diagrams in it were clear and precise about the various options available to the user. The final version will, we understand, be a small booklet with a couple of extra example programs showing how to use the RAM options.

In conclusion, the expansion system performed well and allowed great flexibility in its use. The complete unit costs £47.15 (inclusive) which is not unreasonable compared to similar units for the BBC Micro with less facilities. However, the fact remains that, if you buy this board now, you will have virtually no software to use with it - though we will be producing two ROMs for the Electron shortly - a machine code monitor (EXMON) and a Basic programmers aid (Toolkit). It is also likely that other software in ROM will become available for the Electron now that there is a means of using it.