INT 15 - Advanced Power Management Specification - INSTALLATION CHECK
        AX = 5300h
        BX = 0000h (device ID of system BIOS)
Return: CF clear if successful
            AH = major version (BCD)
            AL = minor version (BCD)
            BX = 504Dh ("PM")
            CX = flags
                bit 0: 16-bit protected mode interface supported
                bit 1: 32-bit protected mode interface supported
                bit 2: CPU idle call reduces processor speed
                bit 3: BIOS power management disabled
                bits 4-7 reserved
        CF set on error
            AH = error code (86h) (see below)

Values for error code:
 01h    power management functionality disabled
 02h    interface connection already in effect
 03h    interface not connected
 04h    real-mode interface not connected
 05h    16-bit protected-mode interface already connected
 06h    16-bit protected-mode interface not supported
 07h    32-bit protected-mode interface already connected
 08h    32-bit protected-mode interface not supported
 09h    unrecognized device ID
 0Ah    invalid parameter value in CX
 0Bh-1Fh reserved for other interface and general errors
 20h-3Fh reserved for CPU errors
 40h-5Fh reserved for device errors
 60h    can't enter requested state
 61h-7Fh reserved for other system errors
 80h    no power management events pending
 81h-85h reserved for other power management event errors
 86h    APM not present
 87h-9Fh reserved for other power management event errors

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