INT 15H: AT Extended Services / APM

 INT 15H handles a set of AT-specific services.

                AH/AX BIOS Service
                ▀▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
                00H   Cassette motor ON ═╗
                01H   Cassette motor OFF ╠═►Oldest PCs only (descriptions
                02H   read cassette      ║  omitted for lack of interest)
                03H   write cassette ════╝

                4fH   keyboard intercept

                53xxH Advanced Power Management (APM) services

            (*) 80H   device open
            (*) 81H   device close
            (*) 82H   program termination
                8300H set event wait interval
                8301H cancel event wait interval
                84H   joystick
            (*) 85H   SysReq key
                86H   wait
                87H   move extended memory block
                88H   get extended memory size
                89H   switch to virtual 8086 mode

            (*) 90H   device busy loop
            (*) 91H   finish interrupt

                c0H   get system configuration

      (*) services marked with (*) are designed for use with multitasking
          operating systems and will only perform the described service if
          they have been intercepted by a multitasking operating system.
          By default (and when MS-DOS is the active system), these fns
          simply clear the Carry Flag and return immediately.

See Also: ROM-BIOS Functions
          BIOS Data Area