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                 EBDA - Extended BIOS Data Area EBDA (PS/2)

      Offset   Size            Description

        00       word      number of bytes allocated to EBDA in Kbytes
        01-21    21bytes   reserved
        22       dword     device driver far call pointer
        26       byte      pointing device flag (1st byte, see below)
        27       byte      pointing device flag (2nd byte, see below)
        28-2F    8 bytes   reserved


              Pointing Device Flag Byte 1

                |7|6|5|4|3|2|1|0| Offset 26
                 | | | | | +------- index count
                 | | | | +-------- reserved (0)
                 | | | +--------- error
                 | | +---------- acknowledge
                 | +----------- resend
                 +------------ command in progress

              Pointing Device Flag Byte 2

                |7|6|5|4|3|2|1|0| Offset 27
                 | | | | | +------- package size
                 | +-------------- reserved
                 +--------------- device driver far call flag


        - EBDA is located in highest memory just under 640K on PS/2
        - word at BIOS Data Area 40:0E is segment address of EBDA