The PSON# signal connects to the ATX PSU Green Wire. When this wire is grounded (Low), the PSU wakes up.
For a detailed visual mapping of the power sequence, including signal timings (oscilloscope graphs) and common voltage rail locations for Intel and AMD boards, download our exclusive diagnostic guide: Frequently Asked Questions (FAQ) What causes the power sequence to fail? desktop motherboard power sequence pdf exclusive
The BIOS begins checking RAM, initializing the GPU, and preparing to boot the operating system. Troubleshooting the Sequence: Common Failure Points Where the Sequence Broke Likely Culprit Dead board; no standby LEDs Blown 5V_SB diode, shorted EC chip, or dead PSU. Fans spin for half a second, then click off Phase 3 / Phase 4 The PSON# signal connects to the ATX PSU Green Wire