Intel 815 Manuel D’Utilisation
Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
R
96
9.3.8. GR06
Miscellaneous Register
I/O (and Memory Offset) Address: 3CFh (Index=06h)
Default:
Default:
0Uh (U=Undefined)
Attributes: Read/Write
7
4
3
2
1 0
Reserved (0000)
Memory Map Mode
Chain
Odd/Even
Graphics /
Text
Mode
Bit Description
7:4
Reserved. Read as 0s.
3:2
Memory Map Mode. These 2 bits control the mapping of the frame buffer into the processor address
space as follows:
space as follows:
Bit [3:2]
Frame Buffer Address Range
00 A0000h
− BFFFFh
01 A0000h
− AFFFFh
10 B0000h
− B7FFFh
11 B8000h
− BFFFFh
Notes:
1. This function is both in standard VGA modes and in extended modes that do not provide linear frame
buffer access.
2. Software must set to the proper value.
1
Chain Odd/Even. This bit provides the ability to alter the interpretation of address bit A0, so that it may
be used in selecting between the odd-numbered memory planes (planes 1 and 3) and the even-
numbered memory planes (planes 0 and 2).
be used in selecting between the odd-numbered memory planes (planes 1 and 3) and the even-
numbered memory planes (planes 0 and 2).
0 = A0 functions normally.
1 = A0 is switched with a high order address bit, in terms of how it is used in address decoding. The
result is that A0 is used to determine which memory plane is being accessed
(A0=0 for planes 0 and 2 and A0=1 for planes 1 and 3).
(A0=0 for planes 0 and 2 and A0=1 for planes 1 and 3).
0
Graphics/Text Mode.
0 = Text mode.
1 = Graphics mode.