Independently Produced Accessories

By Derek Walker

Originally published in EUG #11

ROM128/256 (c)DW Jan 1993

ROM128/256 is a new idea in ROM expansion. Instead of expanding in the normal sideways direction - with its limitations of just sixteen ROMS - eight ROM images per 16k page sit one on top of the other giving a theoretical total of 128 ROMs available within one machine.

The expansion is available in three basic formats:

  1. A ROM128 module which plugs into any 16k socket on the Electron Pres AP6/Slogger AP2, BBC/Master computers. The module has a flying lead terminated in a small selection switch. The switch can be mounted in any convenient place.
  2. A ROM256 cartridge: A Watford Electronics cartridge containing two ROM128 modules with the selection switches mounted on the cartridge or on flying leads (to suit the Slogger RX case).
  3. A ROM128 cartridge, same as ROM256 but with only one ROM128 module built in. There is also one spare 16k socket.

The customer's 8/16K ROMs are transferred into the large ROMs at time of purchase. I must stress that the ROMs to be included in the module must be owned by the customer.

To use, insert the module or cartridge and switch on, one image per module will now be available. To select another image within a module, simply push one of the small buttons on the numbered switch until the desired position is reached. After image selection, a CTRL-BREAK must be issued from the keyboard to initialise the ROM.

There are three major benefits with this expansion:

  1. There is no selection software involved, cutting out any possible problems in that area.
  2. Only one of the eight ROMs is enabled reducing the possibility of ROM clashes.
  3. If a ROM does clash with another simply switch it out - 100% effective.

The ROM256 cartridge is compatible with the Master and the Electron's Plus 1 and AP2 cartridge slots.

The ROM128 module is compatible with any 16k ROM socket within the Master/BBC and Electron AP6/AP2.

Cartridge Conversion
If you have a spare cartridge, get it converted and save buying another cartridge. I can convert most makes of cartridges but some cartridges on the market permit only one selection switch to be mounted on the cartirdge, the other has to be on a short flying lead.

ROM to RAM Cartridge Conversion - Electron Only (c)DW May 1993

A re-designed circuit of a standard ROM cartridge to enable it to accept either ROMs or Static RAM devices - a write protect switch can also be added. Now for the bad news: Unfortunately not all cartridge manufacturers have put the necessary fingers on the edge connectors to enable me to carry out this conversion. So far I have found only quad cartridges to be suitable e.g. Care Electronics and Watford Electronics. Please contact me to confirm suitability.

The modified cartridge will function exactly as before (i.e. as a normal ROM cartridge) but, with suitable RAM devices in place of your ROMs (one RAM replaces one ROM), you will be able to load your own ROM images giving you a more flexible system.

BBRAM (c)DW Aug 1992

A Battery backed RAM module for suitable for the Pres +6 and Slogger's AP2 interfaces. The cartridge gives one 16k bank of sideways RAM in the AP6 and two 16k banks in the AP2. See the article in EUG #6.

STOP PRESS DTP Fonts (c)DW June 1992

Some new fonts for the Stop Press Desk Top Publishing software. These include - MODE 7, the new Teletext character set, the Greek alphabet and numbers, and a few chunky sets suitable for titles. Some of the fonts can be seen in EUG #6.

User Port (c)DW Dec 1992

I have designed a proto-type User Port that fits inside the Plus 1 (thus freeing a cartridge slot) with the connector protruding from the left hand side. I have not taken this project any further as user ports can be obtained from Slogger and Pres - but if there is enough interest I will bring it up to production standards.

Printer Switch (c) DW 1988

This switch redirects the printer output of your computer to either one of two printers and was a project in EUG #5 and #6. A simple modification to the circuit will allow two computers to be switched to one printer.

RGB TTL Switch (c) DW Oct 1993

This fully buffered switch directs the output from either one of two computers to one monitor. Handy if you require two computers on at the same time and a lot cheaper than buying another monitor!

Prices (Oct 1993)

ROM128 Module £17.50
ROM128 Cartridge £28.50
ROM128 Cartridge Conversion£17.50 *
ROM256 Cartridge £45.00
ROM256 Cartridge Conversion£35.00 *
BBRAM Battery Backed RAM module for the Electron AP2/AP6&163;22.95
Nine new Fonts for Stop Press DTP#163;4.00
ROM to RAM Cartridge Conversion£3.00 *
I have a small supply of Static RAMs suitable for the ROM/RAM conversion£5.00 each
User PortPOA
Printer SwitchPOA
RGB TTL Switch£13.00

* = Send your own cartridge for conversion.

Please make cheques or postal orders payable to "Mr D. Walker" and contact me at the address below.

Derek Walker
18 Rannoch Avenue, Bishopbriggs, GLASGOW G64 1BU
EUG #11