When you press the power button, you aren't turning on the power directly; you are sending a request to the Super I/O.
The PCH responds by sending Sleep signals back to the SIO to initiate the transition from sleep states to power-on. PS_ON Activation: desktop motherboard power sequence pdf exclusive
A desktop motherboard power sequence is the rigorous, millisecond-precise order in which voltages and logic signals must activate to transition a system from "Dead" (G3) to "Fully Operational" (S0). When you press the power button, you aren't
The power sequence relies heavily on handshakes—signals sent from one chip to another to say, "I am stable. You may proceed." If these don't rise to 3V after pressing
Unlike free forum threads that contradict each other, this PDF is logically sequenced and error-checked. I’ve already fixed two “dead” boards by tracing missing SLP_S3 using their reference table.
If these don't rise to 3V after pressing the power button, the PCH is typically the point of failure.
The CMOS battery maintains the Real-Time Clock (RTC) and BIOS settings.