## Physical Device Driver Reference

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### POWER_OEMFUNCTION (45h) - GS

GS EAX through GS are input/output parameters representing the corresponding machine registers. These parameters are processed as follows. Before executing the OEM APM call, the register values from the parameter packet are copied to the system's corresponding registers. If segment registers are being used, the current value of DS is saved before overwriting it with the parameter value. The low order word of EAX is set to the value 5380H, regardless of the parameter field value. This is required by the APM specifications for issuing an OEM APM function call. The OEM APM function is then called. Upon return from the OEM APM function call, the current register values are stored in their corresponding fields in the parameter packet. The system's flags are recorded in the Flags parameter field. The DS register, if used, is restored and control is passed back to the caller.