Simon Williams looks at two ROMs for the Beeb that get over the problem of accessibility Product: Sideways ROM cartridge sytem Price: £19.95 (£6.95 per extra cartridge) Distributor: Viglen, Unit 7, Trumpers Way, Hanwell, 01-843 9903 Product: ROM Box Price: £57.45 Distributor: Micro Pulse, Churchfield Road, Frodsham, Cheshire, 0928 35110 Until recently, if you wanted to plug more than three extra ROMs into your BBC Micro you had to buy a ROM expansion board. The trouble with these is that you usually have to wield a screwdriver and take the top off to get at the ROMs.

Systems from Viglen and Micro Pulse get around the problem of accessibility and have the added advantage that they draw no extra power from the computer's supply. Setting Up ---------- In the Viglen system the extra ROMs are contained in cartridges, which are plugged into a socket attached to the BBC in the hole next to the keyboard. This hole, popularly known as the 'ashtray', was left by Acorn to house the ROM cartridges for its speech synthesis system.

The socket is connected to the BBC by a ribbon cable to one of the sideways ROM sockets. Your expansion ROMs fit into carriers that plug into the ashtray socket.

The system comes in kit form consisting of socket with 28-way ribbon cable attached; one cartridge; cover for the socket; cover for the ROM carrier when not in use; and blanking plate to restore the Beeb if you want to take the system out.

The cartridge has two plastic mouldings which screw together to sandwich a small circuit board that contains the ROM of your choice. A notable omission from this otherwise comprehensive kit is a set of labels to stick in the cartridges to identify their components.

The edge-connector that plugs into the socket on the Beeb has one foreshortened contact to ensure that all connections are made before the power is applied to the ROM. Because of this, cartridges can be exchanged freely with the micro switched on. Once in, ROMs are called by pressing Break and then addressed in the normal way.

The Micro Pulse ROM box can hold up to eight integrated circuits (including one in a zero insertion force socket) housed in a metal case with a hinged perspex lid. The box is manufactured to a high standard and uses good-quality components throughout.

Connection to the micro is via a length of ribbon cable with a DIL plug on one end that goes into one of the spare sideways ROM sockets on the Beeb's main board. Operating instructions come on two photocopied sheets and advise inserting the plug into the BBC with the cable facing left and the indexing red stripe to the rear - physically impossible. The cable actually runs out to the right of the machine and connects to the ROM box via a socket in its side.

Clamping the cable to the BBC is achieved by the Heath Robinsonish method of trapping it between the two halves of the case.

Once everything is set up, applying power to the BBC will illuminate one of the eight LEDs. These are used to indicate which of the ROMs is chosen: selection is made by turning the switch fitted to the box. As with the Viglen, the appropriate ROM is enabled by pressing Break, although the instructions on the box suggest the rather more radical CTRL-Break sequence. In Use ------ Each approach to using ROMs external to the Beeb has its pros and cons. Both suffer from the disadvantage that the selected ROM cannot be called without using the Break key first. Using toolkit ROMs in this way could prove awkward, and from Basic you will have to remember to OLD the program under development.

Any software that uses more than one ROM (DataGem, Logo and ISO Pascal, for example) is unusable with both systems since only one ROM is accessible at a time. Verdict ------- The Viglen system is more elegant as there are no trailing leads hanging from the side of the micro when it is not in used. The price quoted for the system includes only one cartridge and you will need one for each ROM.

The Micro Pulse ROM box holds a maximum of eight ROMs, all available at the twist of a switch. Because of its flying lead it is not as neat as the Viglen, and this could cause trouble if the micro is to be moved around. A better method of fixing the lead to the BBC should not be beyond the wit of Micro Pulse's designers. Otherwise, the box seems to be good value.

I will seriously consider getting a Viglen system for ROM software that gets used less frequently. Sideways ROM Cartridge: Report Card ----------------------------------- Features 4/5 Documentation 3/5 Performance 4/5 Overall Value 4/5 ROM box: Report Card -------------------- Features 3/5 Documentation 3/5 Performance 4/5 Overall Value 3/5