The P1 power connector is the first ATX power supplies and motherboards used a single power connector. It also has 20 pins.
A P1 connector is a power connector found on ATX power supplies. It is used to provide main power to the motherboard, and to control ACPI functionality (tell the power suppy to turn off and back on).
P1 connector
P1
P1
20 pin P1 connector.
p1
P1
A regular ATX motherboard uses a single 20-pin P1 connector with optional 4-pin auxillary power connector
ATX version 2.2 allowed for 24-pin P1 connector, which is backward compatible with the 20-pin P1 connector.
24
12v, 3.3v 5v
The expansion slot that requires extra power and added 4 pins to the older 20-pin P1 power connector is the PCI Express (PCIe) slot. The additional 4 pins provide extra power to support higher performance graphics cards and other devices that demand more power than what the standard 20-pin connector can supply. This enhancement allows for improved performance in modern computing systems.