Expects: AX    5301H
BX    0000H (power device ID = System BIOS)
Returns: AH    APM error code (if CF=CY)
Info: This function informs the BIOS that you intend to cooperate with
the BIOS in power management.  For instance, it announces that
you will be making INT 15H 5305H (CPU Idle) and INT 15H 5306H
(CPU Busy) and INT 15H 5307H (Set Power State) calls.

This makes the connection for real-mode.  See INT 15H 5302H or
INT 15H 5303H for protected-mode connection.

You must make a connection via this fn or before using most other
APM API services.  Before you make this call, the BIOS will
supply its own default power management services; you would make
a connection if you think you can do a better job of keeping
track of power in some cases.

See Also: APM API
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INT 15H 5301H: Interface Connect