
82815 GMCH
R
Datasheet
127
PCI Memory Address Range (Top of Main Memory to 4 GB)
The address range from the top of main DRAM to 4 GB (top of physical memory space supported by the
GMCH) is normally mapped via the hub interface to PCI.
As an internal graphics configuration, there are two exceptions to this rule. Both exception cases are
forwarded to the internal graphics device.
The first exception is addresses decoded to the local memory range.
The second exception is addresses decoded to the memory mapped range of the internal graphics
device.
As an AGP configuration, there are two exceptions to this rule.
Addresses decoded to the AGP memory window defined by the MBASE, MLIMIT, PMBASE, and
PMLIMIT registers are mapped to AGP.
Addresses decoded to the graphics aperture range defined by the APBASE and APSIZE registers
are mapped to the main DRAM.
There are two sub-ranges within the PCI memory address range defined as APIC Configuration Space
and High BIOS Address Range.
As an internal graphics device, the Local Memory Range and the
Memory Mapped Range of the internal Graphics Device
MUST NOT
overlap with these two ranges.
Similarly, as an AGP device, the AGP memory window and Graphics Aperture Window
MUST NOT
overlap with these two ranges.
These ranges are described in detail in the following paragraphs.