ATX is the form factor which Motherboards, Computer Cases and Graphics Cards use to standardise sizing. An ATX form-factor Motherboard will fit an ATX Case, and an ATX Graphics Card will fit in the case as well.
the regular ATX has a 20 pin power connector, while the enhanced ATX power connector has 24 pin power connector.
P1 connector
24
20- pin connector
ATX version 2.2 allowed for 24-pin P1 connector, which is backward compatible with the 20-pin P1 connector.
20 pin P1 connector.
Power input connector, or just power connector
Power input connector, or just power connector
P1
enhancer atx motherboard
The atx 12 connector is one of the motherboard power connectors and used for 12 volt power connect for cpu voltage regulator.
ATX