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82815 GMCH
R
Datasheet
123
4.1.2.
Compatibility Area
This area is divided into the following address regions:
0–640 KB DOS Area
640–768 KB Video Buffer Area
768–896 KB in 16KB sections (total of 8 sections) – Expansion Area
896–960 KB in 16KB sections (total of 4 sections) – Extended System BIOS Area
960 KB–1 MB Memory (BIOS Area) – System BIOS Area
The GMCH supports all sixteen memory segments of interest in the compatibility area. Thirteen of the
memory ranges can be enabled or disabled independently for both read and write cycles.
Table 9. Memory Segments and Their Attributes
Memory Segments
Attributes
Comments
000000h–09FFFFh
Fixed; always mapped to main DRAM
0 to 640K: DOS Region
0A0000h–0BFFFFh
mapped to the hub interface or (AGP or internal
graphics) – configurable as SMM space
Video Buffer (physical DRAM
configurable as SMM space)
0C0000h–0C3FFFh
WE RE
Add-on BIOS
0C4000h–0C7FFFh
WE RE
Add-on BIOS
0C8000h–0CBFFFh
WE RE
Add-on BIOS
0CC000h–0CFFFFh
WE RE
Add-on BIOS
0D0000h–0D3FFFh
WE RE
Add-on BIOS
0D4000h–0D7FFFh
WE RE
Add-on BIOS
0D8000h–0DBFFFh
WE RE
Add-on BIOS
0DC000h–0DFFFFh
WE RE
Add-on BIOS
0E0000h–0E3FFFh
WE RE
BIOS Extension
0E4000h–0E7FFFh
WE RE
BIOS Extension
0E8000h–0EBFFFh
WE RE
BIOS Extension
0EC000h–0EFFFFh
WE RE
BIOS Extension
0F0000h–0FFFFFh
WE RE
BIOS Area
DOS Area (00000h–9FFFh)
The DOS area is 640 KB and is always mapped to the main memory controlled by the GMCH.