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Register Description
D15343-003 59
4.8.14 GGC – GMCH Graphics Control Register (Device #0)
Address Offset:
Default Value:
Access:
Size:
52-53h
0030h
Read/Write
16 bits
Bit Descriptions
15:7 Reserved
6:4 Graphics Mode Select (GMS): This field is used to select the amount of Main system memory
that is pre-allocated to support the Internal Graphics Device in VGA (non-linear) and Native (linear)
modes. The BIOS ensures that system memory is pre-allocated only when Internal Graphics is
enabled.
000: No system memory pre-allocated. Device #2 (IGD) does not claim VGA cycles (Memory and
I/O), and the Sub-Class Code field within Device #2 Function #0 Class Code register is 80.
001: DVMT (UMA) mode, 1 MB of system memory pre-allocated for frame buffer.
010: DVMT (UMA) mode, 4 MB of system memory pre-allocated for frame buffer.
011: DVMT (UMA) mode, 8 MB of system memory pre-allocated for frame buffer.
100: DVMT (UMA) mode, 16 MB of system memory pre-allocated for frame buffer.
101: DVMT (UMA) mode, 32 MB of system memory pre-allocated for frame buffer.
All other combinations reserved.
3 Reserved
2 Device #2 Function #1 Enable/Disable:
1: Disable Function #1 within Device #2.
0: Enable Function #1 within Device #2.
1 IGD VGA Disable (IVD): VGA can only be enabled in Naytive Graphics Mode. If strapped in other
mode, this bit should always set to 1.
1: Disable. Device #2 (IGD) does not claim VGA Memory and I/O Mem cycles, and the Sub-Class
Code field within Device #2 Function #0 Class Code register is 80.
0: Enable. Device #2 (IGD) claims VGA Memory and I/O cycles, the Sub-Class Code within Device
#2 Class Code register is 00.
0 Reserved