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Intel® 945G/945GZ/945GC/ 945P/945PL Express Chipset Family ...

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Compatible SMRAM Address Range (A_0000h–B_FFFFh)<br />

System Address Map<br />

When compatible SMM space is enabled, SMM-mode processor accesses to this range are routed<br />

to physical system DRAM at 000A 0000h –000B FFFFh. Non-SMM-mode processor accesses to<br />

this range are considered to be to the video buffer area as previously described. PCI <strong>Express</strong> and<br />

DMI-originated cycles to enabled SMM space are not allowed and are considered to be to the<br />

video buffer area if IGD (82<strong>945G</strong>/82<strong>945G</strong>C/82<strong>945G</strong>Z GMCH on ly) is not enabled as the VGA<br />

device. PCI <strong>Express</strong> and DMI initiated cycles are attempted as peer cycles, and will master abort<br />

on PCI if no external VGA device claims them.<br />

Monochrome Adapter (MDA) Range (B_0000h–B_7FFFh)<br />

Legacy support requires the ability to have a second graphics controller (monochrome) in the<br />

system. Accesses in the standard VGA range are forwarded to IGD, PCI <strong>Express</strong>, or the DMI<br />

(depending on configuration bits). Since the monochrome adapter may be mapped to any one of<br />

these devices, the (G)MCH must decode cycles in the MDA range (000B_0000h – 000B_7FFFh)<br />

and forward either to IGD, PCI <strong>Express</strong>, or the DMI. This capability is controlled by a VGA<br />

steering bits and the legacy configuration bit (MDAP bit). In addition to the memory range<br />

B0000h to B7FFFh, the (G)MCH decodes I/O cycles at 3B4h, 3B5h, 3B8h, 3B9h, 3BAh, and<br />

3BFh and forwards them to the either IGD, PCI <strong>Express</strong>, and/or the DMI.<br />

9.1.3 Expansion Area (C_0000h–D_FFFFh)<br />

This 128-KB ISA Expansion region (000C_0000h – 000D_FFFFh) is divided into eight 16-KB<br />

segments. Each segment can be assigned one of four read/write states: read only, write only,<br />

read/write, or disabled. Typically, these blocks are mapped through (G)MCH and are<br />

subtractively decoded to ISA space. Memory that is disabled is not remapped.<br />

Non-snooped accesses from PCI <strong>Express</strong> or DMI to this region are always sent to main memory.<br />

Table 9-1. Expansion Area Memory Segments<br />

Memory Segments Attributes Comments<br />

0C0000h–0C3FFFh W/R Add-on BIOS<br />

0C4000h–0C7FFFh W/R Add-on BIOS<br />

0C8000h–0CBFFFh W/R Add-on BIOS<br />

0CC000h–0CFFFFh W/R Add-on BIOS<br />

0D0000h–0D3FFFh W/R Add-on BIOS<br />

0D4000h–0D7FFFh W/R Add-on BIOS<br />

0D8000h–0DBFFFh W/R Add-on BIOS<br />

0DC000h–0DFFFFh W/R Add-on BIOS<br />

Intel ® 82<strong>945G</strong>/82<strong>945G</strong>/82<strong>945G</strong>C GMCH and 82<strong>945P</strong>/82<strong>945P</strong>L MCH Datasheet 209

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