845GL datasheet(66/193 Pages) INTEL

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Intel® 82845G/82845GL/82845GV GMCH Datasheet

Microsoft MS-DOS* Application Area (00000h–9FFFh)

The MS-DOS* area is 640 KB in size and it is further divided into two parts. The 512-KB area at 0

to 7FFFFh is always mapped to the main memory controlled by the GMCH, while the 128-KB

address range from 080000h to 09FFFFh can be mapped to PCI_A or to main DRAM. By default

this range is mapped to main memory and can be declared as a main memory hole (accesses

forwarded to PCI_A) via the GMCH FDHC configuration register.

Video Buffer Area (A0000h–BFFFFh)

Attribute bits do not control this 128-KB area. The host -initiated cycles in this region are always

forwarded to either PCI_A or AGP unless this range is accessed in SMM mode. Routing of

accesses is controlled by the Legacy VGA control mechanism of the “virtual” PCI-to-PCI

bridge device embedded within the GMCH.

This area can be programmed as SMM area via the SMRAM register. When used as a SMM space,

this range cannot be accessed from the hub interface or AGP.

Expansion Area (C0000h–DFFFFh)

This 128-KB area is divided into eight, 16-KB segments that can be assigned with different

attributes via the PAM Control registers as defined by Table 3-2.

Extended System BIOS Area (E0000h–EFFFFh)

This 64-KB area is divided into four, 16-KB segments that can be assigned with different attributes

via the PAM Control registers as defined by Table 3-2.

System BIOS Area (F0000h–FFFFFh)

This area is a single, 64-KB segment, which can be assigned with different attributes via the PAM

Control registers as defined by Table 3-2.

845GL Datasheet(PDF) 66 Page - Intel Corporation