0:413h                   Memory Size in Kilobytes (0-640)

 Length: 2 bytes

    Contains the number of contiguous 1K memory blocks in the system (up
    to 640K).

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       Notes:         Use INT 12h to access the memory size using the ROM
                      BIOS interface.

                      This memory value is determined at power-on time by
                      either examining the DIP switches on the system
                      board or using the value stored in the CMOS battery,
                      whichever way is appropriate according to the type
                      of machine.

                      This is the amount of memory available to the entire
                      system. This is not the amount of memory available
                      to the user's program. Use INT 21h, Function 48h, to
                      determine the amount of memory available to a user's
                      program.

                      To determine the amount of memory above the 1024K
                      address range, use INT 15h, Service 88h.

                      If the CMOS battery memory value or the DIP switch
                      value is greater than the actual amount of memory,
                      then the actual amount of memory is returned by this
                      interrupt.