Intel 815 Manuel D’Utilisation
Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0
R
139
9.6.38. CR70
Interlace Control Register
I/O (and Memory Offset) Address: 3B5h/3D5h (index=70h)
Default: 00h
Attributes: Read/Write
Default: 00h
Attributes: Read/Write
7
6
0
Interlace
Enable
CRT Half-Line Value
Bit Description
7
Interlace Enable.
0 = Selects non-interlaced CRT output (default).
1 = Selects interlaced CRT output.
6:0
CRT Half-Line Value. When interlaced CRT output has been selected, the value in this register
specifies the position along the length of a scan line at which the half-line vertical sync pulse occurs for
the odd frame. This half-line vertical sync pulse begins at a position between two horizontal sync pulses
on the last scan line, rather than coincident with the beginning of a horizontal sync pulse at the end of a
scan line.
specifies the position along the length of a scan line at which the half-line vertical sync pulse occurs for
the odd frame. This half-line vertical sync pulse begins at a position between two horizontal sync pulses
on the last scan line, rather than coincident with the beginning of a horizontal sync pulse at the end of a
scan line.
9.6.39. CR80
I/O Control
I/O (and Memory Offset) Address: 3B5h/3D5h(index 80h)
Default: 00h
Attributes: Read/Write
Default: 00h
Attributes: Read/Write
7
2
1 0
Reserved (000000)
Attr Cntl
Ext Enbl
CRT Cntl
Int Enbl
Bit Description
7:2
Reserved.
1
Attribute Controller Extensions Enable. Controls whether the attribute registers are accessed with
both index and data at 3C0h (strict VGA mode), or whether they are accessed with 3c0h as the index
and 3C1h is data. It is possible that BIOS software or driver software might not use the non-VGA mode.
Either method should work, but it needs to be the method the software is using.
both index and data at 3C0h (strict VGA mode), or whether they are accessed with 3c0h as the index
and 3C1h is data. It is possible that BIOS software or driver software might not use the non-VGA mode.
Either method should work, but it needs to be the method the software is using.
0 = Disable, i.e., strictly VGA compatible mode (default)
1 = Enable Attribute Controller extensions
Index and Data of the Attribute Controller registers are accessible at 3C0h in standard VGA. When the
Attribute Controller Extensions are enabled, Index and Data are accessible at addresses 3C0h and
3C1h, respectively.
Attribute Controller Extensions are enabled, Index and Data are accessible at addresses 3C0h and
3C1h, respectively.
0
CRT Controller Interpretation Enable. This bit modifies responses/functionality to registers CR30 and
beyond, except for CR41.
beyond, except for CR41.
0 = Registers have strict VGA Interpretation (default)
1 = Registers have extended VGA Interpretation (i.e., access to 4G space)