Intel 925 Data Sheet - Page 159
DOS Range 0h - 9_FFFFh, Legacy Video Area A_0000h-B_FFFFh
UPC - 683728067724
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Page 159 highlights
System Address Map R Figure 9-2. Microsoft MS-DOS* Legacy Address Range 000F_FFFFh 000F_0000h 000E_FFFFh 000E_0000h 000D_FFFFh 000C_0000h 000B_FFFFh 000A_0000h 0009_FFFFh System BIOS (Upper) 64KB Extended System BIOS (Lower) 64KB (16KBx4) Expansion Area 128KB (16KBx8) Legacy Video Area (SMM Memory) 128KB 1MB 960KB 896KB 768KB 640KB DOS Area 0000_0000h 9.1.1 9.1.2 DOS Range (0h - 9_FFFFh) The DOS area is 640 KB (0000_0000h - 0009_FFFFh) in size and is always mapped to the main memory controlled by the MCH. Legacy Video Area (A_0000h-B_FFFFh) The legacy 128-KB VGA memory range, frame buffer, (000A_0000h - 000B_FFFFh) can be mapped to PCI Express and/or to the DMI. The appropriate mapping is programmable. Based on the programming, priority for VGA mapping is constant. The MCH always decodes internally mapped devices first. The MCH always positively decodes internally mapped devices, namely the PCI Express. Subsequent decoding of regions mapped to PCI Express or the DMI depends on the programming. This region is also the default for SMM space. Intel® 82925X/82925XE MCH Datasheet 159