Intel 815 manual Red, Green Blue

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

R

These registers determine the characteristics of the gamma correction for the overlay data. Each register is 32 bits wide. The registers are written to and read from together when accessed from the PCI.

The GAMCxx registers are not double buffered and should only be updated when the Overlay Engine is disabled. During operation, the bytes of these registers are read independently. These registers are dependent on the R, G, or B pixel values.

There are several restrictions when using gamma values. The restrictions are:

•Gamma curve should be always a rising curve

•GAMC0 cannot have value of 0

•Difference between the two adjacent gamma registers cannot be greater than 0x7F

31	24	23	16	15	8	7	0
	Reserved	Red		Green			Blue
Bit				Description
31:24	Reserved.
23:16	Red.
15:8	Green.
7:0	Blue.
	GAMC5: Used of bit <7:6> = 11
	GAMC4: Used of bits <7:6> = 10
	GAMC3: Used of bits <7:6> = 01
	GAMC2: Used of bits <7:5> = 001
	GAMC1: Used of bits <7:4> = 0001
	GAMC0: Used of bits <7:3> = 00001

270