Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

R

 

Bit

Descriptions

 

 

 

 

0

GUI Mode.

 

 

0 = Standard VGA and extended 4 bpp/16 color resolutions (default). Can still access memory in linear

 

 

mode.

 

 

1 = High Resolution (i.e., not VGA or extended planar).

 

 

Transition from VGA modes to hires mode or opposite:

 

 

Software will turn the display engine off (screen off) using SR01[Screen Off] and wait for at least two

 

 

HSYNC periods and no more than two VSYNC periods (since one of the isochronous streams is

 

 

DRAM refresh (controlled by DRAMCXH[DRAM Refresh Status]), the wait should not be so long as to

 

 

cause the DRAM content to degrade) before writing to PIXCONF[0] and turning the display on. This

 

 

should ensure that all the data requested from the display engine will be out of the local memory

 

 

interface before PIXCONF is touched. In addition, while switching from hi-res to VGA or VGA to hi-res,

 

 

software will ensure that all the other isochronous streams are off before programming PIXCONF[0].

 

 

 

 

NOTES:

Bits [27:24] are not normally used by the graphics BIOS or by the drivers because the gamma values are

 

 

specific to a particular display device, and apply to two color or hi-color modes (16 and 24 bit). It is

 

 

necessary to program the palette first with the gamma adjusted values. There is only one palette, so if

 

 

both 3:2 are set, they have the same gamma adjustments. Typical code and typical drivers leave these

 

 

bits as zero.

20.3.2.BLTCNTL—BLT Control

Memory Offset Address:

7000Ch

 

 

Default:

 

0000h

 

 

Attributes:

Read/Write

 

 

15

 

1

0

 

 

 

 

 

Reserved

BLT

 

 

 

 

 

 

Status

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit

 

Descriptions

 

 

 

 

 

 

 

 

 

15:1

Reserved.

 

 

 

 

 

 

 

 

 

0

BLT Status – RO. This read-only bit reflects the busy status of BLT Engine only.

 

 

 

 

 

0 = Idle (default)

 

 

 

 

 

 

1 = Busy

 

 

 

 

 

 

 

 

 

 

20.3.3.SWF[1:3]—Software Flag Registers

Memory Offset Address:

SWF1 =70014h

 

SWF2 = 70018h

 

SWF3 = 7001Ch

Default:

00000000h

Attributes:

Read/Write

These 32-bit registers are used as scratch pad space in BIOS, and have no effect on hardware.

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Intel 815 manual BLTCNTL-BLT Control, SWF13-Software Flag Registers, GUI Mode