82830MP Datasheet, PDF (99/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel^® 830MP Chipset
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5 Functional Description
5.1
5.1.1
System Address Map
An Intel^® Pentium^® III Processor-M system based on the 830MP GMCH-M supports 4 GB of
addressable memory space and 64 KB+3 of addressable I/O space. (The P6 bus I/O addressability is 64
KB + 3.) There is a programmable memory address space under the 1 MB region that is divided into
regions which can be individually controlled with programmable attributes such as Disable, Read/Write,
Write Only, or Read Only.
The Intel Pentium III Processor-M family supports addressing of memory ranges larger than 4 GB. The
GMCH-M claims any CPU access over 4 GB and terminates the transaction without forwarding it to hub
interface or AGP. Simply dropping the data terminates writes and for reads the GMCH-M returns all
zeros on the host bus. Note that the 830MP platform does not support the PCI Dual Address Cycle
Mechanism (DAC) and therefore does not allow addressing of greater than 4 GB on either the hub
interface or AGP interface.
In the following sections, it is assumed that all of the compatibility memory ranges reside on the hub
interface/PCI. The exception to this rule is VGA ranges, which may be mapped to AGP. In the absence
of more specific references, cycle descriptions referencing PCI should be interpreted as the hub
interface/PCI, while cycle descriptions referencing AGP are related to the AGP bus.
System Memory Address Ranges
The GMCH-M provides a maximum PC133 address decode space of 1.0 GB. The GMCH-M does not
re-map APIC memory space. The GMCH-M does not limit SDRAM space in hardware. It is the BIOS
or system designer’s responsibility to limit SDRAM population so that adequate PCI, AGP, High
BIOS, and APIC memory space can be allocated. The following figure represents system memory
address map in a simplified form. The following figure provides additional details on mapping specific
memory regions as defined and supported by the Intel 830MP chipset.
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Datasheet
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