The schematic clearly outlines the rails. On the MBX252, the RTC cell powers the CMOS. When the AC adapter is plugged in, the +3.3V_ALW and +5V_ALW are generated by the MAX8734A or similar PWM chip. The schematic shows the exact resistor dividers for the adapter detection (ACOK) signal. A common fault here is a failed capacitor on the LDO output.

An overview of how the CPU, Northbridge/Southbridge (or APU), and I/O controllers interact. Power Distribution:

– Download datasheets for main ICs (e.g., PU2 = RT8205, PU5 = ISL6237) and draw local power circuits yourself.