Intel 815 manual 22. CR14Underline Location Register, CR146 CR176 Addressing Mode, Count By

Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

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9.6.22.CR14Underline Location Register

I/O (and Memory Offset) Address:										3B5h/3D5h (index=14h)
Default:										0UUU UUUUb (U=Undefined)
Attributes:										Read/Write
7					6		5		4		0
		Reserved				DWord		Count By		Underline Location
		(0)				Mode		4
		Bit								Description
	7		Reserved. Read as 0s.
	6		DWord Mode.
			0	= Frame buffer addresses are interpreted by the frame buffer address decoder as being either byte
					addresses or word addresses, depending on the setting of bit 6 of the CRT Mode Control Register
					(CR17).
			1	= Frame buffer addresses are interpreted by the frame buffer address decoder as being DWord
					addresses, regardless of the setting of bit 6 of the CRT Mode Control Register (CR17).
			Note that this bit is used in conjunction with bits 6 and 5 of the CRT Mode Control Register (CR17) to
			select how frame buffer addresses from the processor are interpreted by the frame buffer address
			decoder as shown below:
			CR14[6]				CR17[6]		Addressing Mode
			0				0		Word Mode
			0				1		Byte Mode
			1				0		DWord Mode
			1				1		DWord Mode
	5		Count By 4.
			0	= The memory address counter is incremented either every character clock or every other character
						clock, depending upon the setting of bit 3 of the CRT Mode Control Register.
			1	= The memory address counter is incremented either every 4 character clocks or every 2 character
						clocks, depending upon the setting of bit 3 of the CRT Mode Control Register.
			Note that this bit is used in conjunction with bit 3 of the CRT Mode Control Register (CR17) to select the
			number of character clocks are required to cause the memory address counter to be incremented as
			shown, below:
			CR14[5]				CR17[3]		Address Incrementing Interval
			0				0		every character clock
			0				1		every 2 character clocks
			1				0		every 4 character clocks
			1				1		every 2 character clocks
	4:0		Underline Location. This field specifies which horizontal line of pixels in a character box is to be used
			to display a character underline in text mode. The horizontal lines of pixels in a character box are
			numbered from top to bottom, with the top-most line being number 0. The value specified by these 5 bits
			should be the number of the horizontal line on which the character underline mark is to be shown.

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