One of the first, and now the most common, way of expanding the basic Electron and Plus 1 is with a ROM expansion board of some sort.

There are two main types: Those that fit insde the Plus 1, like the AP6, reviewed in the May 1988 issue of Electron User, and those that plug into one of the two cartridge sockets.

This latter type is by far the most common, and now Jafa Systems has added its own cartridge - the ROMPLUS-144 - to the half dozen or so already available. So what advantages does this offer?

The problem with ROM expansion boards that plug into the cartridge slots in that only two ROMs can be mapped into each. The rear socket can hold ROMs zero and one, while the front socket can hold ROMs two and three.

The Jafa cartridge, constructed in matching Acorn cream plastic, contains nine sockets. One houses the ROMPLUS-144 Operating System, and in the review cartridge another contained a 32K RAM chip - an optional extra.

This leaves seven sockets free for your ROMs. However, the Electron will only allow two ROMs per cartridge slot. The purpose of the ROMPLUS Operating System - which occupies one position - is to control selection of one of the seven other ROMs, or the RAM chip.

There are several new star commands, and *HELP ROMEX prints a list, plus all the ROMs present. To select a ROM, *RSELECT is used. This resets the Electron, so care is needed when using it.

The Help message of any ROM can be printed with *RHELP, and a command passed to a non-selected ROM with *RCOMMAND. A ROM can be disassembled with a fairly basic utility called with *RDISASSEMBLER, and can be saved to disc or tape with *RSAVE.

You can load ROM images into the 32K RAM chip with *RLOAD, and then the chip can be selected like any other ROM.

Two 16K ROMs can be loaded into the 32K RAM with *RSUBSTITUTE, and this command locks out the ROMPLUS Operating System, enabling both RAM-based ROMs to be initialised.

The 32K RAM in the ROMPLUS can be used as a RAM disc, emulating the ROM filing system. Its small size severely limits its usefulness, but for what it's worth, you can *BUILD text files, print them with *TYPE, copy from/to tape or disc with *COPY and *DUMP, and delete files with *DELETE.

These commands are filing system sensitive. So if you've selected the disc filing system, the RAM commands are ignored, and are only used when the ROM filing system is selected with *ROM.

Alternatively, you can use the RAM as a 16K printer buffer. It is selected with the command *RBUFFER, and cleared with *RPURGE. A large printer buffer enables you to carry on working while printing a large text file or program listing.

I liked the ROMPLUS-144, though it does have its faults. Like all other cartridge-based ROM expansion units, it takes up a valuable slot that you might need for a disc drive, user port and so on. And the screws in the ROMPLUS-144 case were so large that I had to remove them to get it to slide into the slot!

A utility for saving ROMs isn't included with the hardware, and this could pose problems for some users trying to save cartridges like VIEW, or LOGO, to disc. However, Jafa can provide one for an additional £2. I would like to see this included with the hardware, particularly the ROMPLUS-144 with RAM option fitted.

A minor improvement could be made when cataloguing the RAM disc. The free space in bytes is printed in hex, and would be better in decimal.

These niggles are quite minor, and the ROMPLUS-144 is an excellent add-on for anyone wishing to expand the capabilities of their Electron and Plus 1.