About this TechDoc

This guide is designed to assist people in the installation of a BJL ROM into a stock Atari Jaguar. You could also use this guide for installing other ROM's if you wish, but I will only cover the installation of a BJL ROM here.

DISCLAIMER : I accept no responcibility for any damage you cause to yourself or your equipment through the use and/or missuse of this guide. If you don't know the hot end from the cold end of a soldering iron. STOP NOW!

What is BJL?

BJL (or Behind Jaggy Lines) is a cheap alternative method of programming the Atari Jaguar console. It is considerably cheaper and easier to get hold of than say an Alpine development system, there are benifits to using an Alpine, but if you are not sure you would get the use out of an Alpine, or just want to dabble, then BJL is perfect.

BJL was developed by Bastian Schick many moons ago. It works by allowing the user to upload code directly into the Jaguars internal 2 MegaBtyes of RAM, via the second controller port. This may sound a bit ropey, but it works VERY well. A special cable is required to connect the controller port to the parallel port of a computer. With the BJL ROM you no-longer get the Atari logo and spinning cube, instead you get a text display with CPU registers displayed, and several options. On the ROM come some nice small games written by various underground developers, also there is an option to boot the cartridge that is plugged into the jag. Then there are 2 different types of upload availible, 4 bit and 8 bit.

Some people have installed their BJL ROM on a switch system so they can switch between the original Atari boot ROM and the BJL ROM, I don't find this necissary as I can run all my games with the BJL ROM, so this guide will explain the approach I have taken, which involves the removal of the original ROM chip.

Equipment needed to do the mod