Multiple choice hardware What is different between AT and ATX power supplies? They are identical except for their shape. AT supplies use a single P1 power connector while ATX uses P8 and P9. AT power supplies run on 120V AC current while ATX uses 220V AC AT supplies use P8 and P9 power connectors while ATX uses a single P1 connector. Reveal answer Fill a bubble to check yourself D Correct answer Explanation AT power supplies use two separate connectors (P8 and P9) that must be plugged in carefully with black grounds together. ATX uses a single P1 connector with 20 or 24 pins. They operate on the same voltage.