ATX 20-Pin Power Supply Connector

This is the standard 20-pin ATX power connector used by many systems. It supplies all core system voltages including +3.3V, +5V, +12V, and -12V, along with necessary control signals such as PWR_OK and PS_ON. It is available on typical ATX power supplies from the late 1990s to early 2000s.

Pinout:

Pin	Signal	Description
1	+3.3V	+3.3 VDC
2	+3.3V	+3.3 VDC
3	GND	Chassis ground
4	+5V	+5 VDC
5	GND	Chassis ground
6	+5V	+5 VDC
7	GND	Chassis ground
8	PWR_OK	Power good
9	+5VSB	+5V standby
10	+12V	+12 VDC
11	+3.3V	+3.3 VDC
12	-12V	-12 VDC
13	GND	Chassis ground
14	PS_ON	Power supply on
15	GND	Chassis ground
16	GND	Chassis ground
17	GND	Chassis ground
18	-5V	-5 VDC (legacy)
19	+5V	+5 VDC
20	+5V	+5 VDC

Notes:

• +5VSB (Pin 9) provides standby voltage used by power management features.
• PS_ON (Pin 14) is a control line used to turn on the PSU via motherboard logic.
• PWR_OK (Pin 8) signals when power is stable and within spec.
• -5V (Pin 18) is used for ISA bus compatibility and is typically unused in modern systems.