Datasheet

Intel Desktop Board D865GBF/D865GLC Technical Product Specification
60
program will further reduce the amount of memory available to the operating system. Figure 17
shows a schematic of the system memory map. All installed system memory can be used when
there is no overlap of system addresses. For example, all of the system address space can be
utilized on a system that has 2 GB of installed system memory, AGP aperture set for 256 MB, and
the PCI cards are requesting 200 MB of system address space.
Upper BIOS
area (64 KB)
Lower BIOS
area
(64 KB;
16 KB x 4)
Add-in Card
BIOS and
Buffer area
(128 KB;
16 KB x 8)
Standard PCI/
ISA Video
Memory (SMM
Memory)
128 KB *
DOS area
(640 KB)
1 MB
960 KB
896 KB
768 KB
640 KB
0 KB
0FFFFFH
0F0000H
0EFFFFH
0E0000H
0DFFFFH
0C0000H
0BFFFFH
0A0000H
09FFFFH
00000H
* Optionally mapped
to the internal AGP
FLASH
APIC
Reserved
Video Frame
Buffer
0 MB
640 KB
1 MB
Top of usable
DRAM (memory
visible to the
operating
system)
Top of installed
DRAM
PCI Memory
Range
(Contains
AGP window,
GFX aperture,
PCI, and ICH
ranges)
DOS
Compatibility
Memory
DRAM
Range
OM15972
~20 MB
4 GB
Top of System Address Space
Figure 17. Detailed System Memory Address Map