Warning: Do this at your own risk. I will not be responsible for any issues. Make sure nothing is connected to electricity when doing this.(i,e. make sure everything is completely unconnected). If you do not, you will get electrocuted and die, so use common sense and be careful so you do not kill your working power supply and computer either. If you feel uncomfortable doing this, then get a professional to help you. Preferably you should not be color blind. You must know how to solder. Take your time making this cable.
To me the cable was not that hard to make but it did take a while. I also had to make sure of the safety precautions so no one or nothing was hurt and that I was accurate in connecting the wires..
Step 1: Whats needed.
1 - AT Computer and monitor
1 - ATX to ATX cable Extension (Available a better computer stores)
1 - set AT wires (p8/p9) set from a dead AT power supply.
1 - Toggle On/Off switch (not a momentary switch).
Wiring diagrams for your ATX and AT power supplies. Yours may vary, so be careful. You may have to set up your own wiring conversion diagram. Mine is ONLY for the power supplies I used.