INT 15 - Advanced Power Management v1.0+ - INSTALLATION CHECK
AX = 5300h
BX = device ID of system BIOS (0000h)
Return: CF clear if successful
AH = major version (BCD)
AL = minor version (BCD)
BX = 504Dh ("PM")
CX = flags (see #00472)
CF set on error
AH = error code (06h,09h,86h) (see #00473)
BUG: early versions of the Award Modular BIOS with built-in APM support
reportedly do not set BX on return