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Intel
®
82854 GMCH System Address Map
D15343-003 111
5.0 Intel
®
82854 GMCH System Address Map
A system based on the GMCH supports 4 GB of addressable system memory space and 64 kB+3B
of addressable I/O space. The I/O and system memory spaces are divided by system configuration
software into regions. The system memory ranges are useful either as system memory or as
specialized system memory, while the I/O regions are used solely to control the operation of
devices in the system.
When the GMCH receives a Write request whose address targets an invalid space, the data is
ignored. For Reads, the GMCH responds by returning all zeros on the requesting interface.
5.1 System Memory Address Ranges
The GMCH provides a maximum system memory of 2 GB. The GMCH does not remap APIC
memory space and does not limit DDR SDRAM space in hardware. It is the BIOS or system
designer's responsibility to limit system memory population so that adequate PCI High BIOS and
APIC memory space can be allocated. Figure 5 and Figure 6 depict the system memory address
map in a simplified form and provide details on mapping specific system memory regions as
defined and supported by the GMCH.
Figure 5. Simplified View of System Address Map
Independently
Programmable
Non-Overlapping
Memory Windows
Main
Memory
Address
Range
Graphics
Memory
Address
Range
4 GB
Top of the
Main Memory
0
Graphic
(Local)
Memory