The importance of ALL_SYS_PWRGD signal in apple laptop

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Ermansha
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The importance of ALL_SYS_PWRGD signal in apple laptop

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Apple has developed a complex validation mechanism to ensure all the power rails being created are stable and good (GD stands for good) for use. If all the power rails are good, then a valid ALL_SYS_PWRGD signal will be produced. ALL_SYS_PWRGD voltage is 3.3V.

A valid ALL_SYS_PWRGD signal checks these power rails: PP1V8_S3, PP5V_S3, PP1V2_S3, PP1V05_S0, PP5V_S0, PP3V3_S0, PP1V5_S0. Any of these S3 or S0 state power rails malfunction will pull down the ALL_SYS_PWRGD signal and terminate the normal power-on process of Apple computers.
The ALL_SYS_PWRGD signal will be reported to SMC. SMC will process this signal and prepare to create the last power rail – CPU/PCH Vcore power rail.
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