User's Manual

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
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356
Bit Descriptions
19:16 Display Color Mode.
0000 = CRT standard VGA text and graphics mode and 1-bit/2-bit/4-bit packed graphics mode
(Default).
0001 = Reserved.
0010 = CRT 8-bit packed extended graphics mode.
0011 = Reserved.
0100 = CRT 16-bit packed (5-5-5) extended graphics mode (Targa compatible).
0101 = CRT 16-bit packed (5-6-5) extended graphics mode (XGA compatible).
0110 = CRT 24-bit extended graphics mode compressed.
0111 = CRT 24-bit extended graphics mode uncompressed. In this mode, pixels are stored only on the
lower three bytes (plane 0,1,2) of each double word and the most significant byte of each
double word (plane 3) is not used.
15 8-Bit DAC Enable.
0 = 6-bit DAC (default).
1 = 8-bit DAC.
14:13 Reserved.
12 Hardware Cursor Display Enable. Software should always set this bit to 1. The setting of this bit to 1
should not do any harm even while in VGA mode.
0 = Disable (default).
1 = Enable.
11 Enable Extended Status Read Mode.
0 = Disable (default).
1 = With this bit enabled, the status of the internal state machines and values of the red and green
data in the input holding register through the normal DAC register ports is available. The register
ports are redefined as follows when this bit is set:
DACMASK = Returns red input data holding value
DACWX = Returns green input data holding value
DACSTATE = Returns the status of the internal state machines in bits [7:2]
10 CRT Overscan Color
0 = Disable (default).
1 = Enable Protected CRT Overscan Color (Overscan[0]).
9 Reserved.
8 Palette Addressing.
0 = Disable (default).
1 = Enable Extended Palette Addressing (Enables access to all 8 locations).
7:2 Reserved (000000).
1 VGA Wrap.
0 = 256 KB wrap state (default) for memory starting at A0000.
1 = Do not wrap.