Int 15 Fn 5300  - Advanced Power Management Specification - Installation   [p]

   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