Online HelpPC 2.10 Quick Reference Utility Copyright 1991 David Jurgens
GDT - Global Descriptor Table
Offset Size Description
00 8bytes dummy, set to 0
08 8bytes GDT data segment location, set to 0
10 8bytes source GDT pointer
18 8bytes target GDT pointer
20 8bytes pointer to BIOS code segment, set to 0. used by
the BIOS to create protected mode code segment
28 8bytes pointer to BIOS stack segment, set to 0. Used by
the BIOS to create protected mode stack segment
30 8bytes user code segment
38 8bytes temporary BIOS code segment
Source/Target GDT use the following format (offsets 10h and 18h):
Offset Size Description
00 word Segment limit
02 3bytes 24 bit segment physical address
05 byte data access rights, set to 93h
06 word reserved word, must be 0
- see LGDT SGDT
[helppc.bosbyte.nl] Global Descriptor Table