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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

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

Pointing Device Flag Byte 2

bit Offset 27
0-2 package size
3-6 reserved
7 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
back2root/ibm-pc-ms-dos/hardware/informations/edba.txt · Dernière modification : 2023/01/16 18:03 de frater