Can you help me with the math, tell me if you think I am right or wrong:
13 amps per pin x 2 pins x 12 volts = 312 watts.
...
Any thoughts?
Thanks for all the help so far!
Apparently for a 24pin connector. 18 gauge wire, the limit is 8.0 Amps.
On another wikipedia page, it is mentioned that the current rating given assumes a 30°C temperature rise (not sure where to find a citation). That means that if your machine is running at 40°C, your cables will be at 70°C. Depending on the cable, the wire insulation may melt at only 85°C. Edit: I think most chassis wiring is rated for 105°C. In any case, it is usually printed on the cable.
I worked out a possible fix: If you are able to find a way to disconnect the wires from the connector, you can put heat-shrink tubing over each wire (assuming you found any breaks). I was able to do that once while converting an old DELL supply to the ATX standard. Tried again years later and was not able to do it. IIRC, the pins use springs to stay in place.
The limit I have been using for ATX power: 5 amps per wire pair.
Edit: splitters are bad news. You want wire pairs going all the way back to the PSU.