Intel 815 manual 2. SR00Sequencer Reset

Models: 815

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Intel® 815 Chipset: Graphics Controller PRM, Rev 1.0

R

9.2.2.SR00Sequencer Reset

I/O (and Memory Offset) Address:

3C5h(Index=00h)

 

 

 

Default:

 

00h

 

 

 

Attributes:

Read/Write

 

 

 

7

 

2

1

0

 

 

 

 

Reserved (000000)

Reserved

Reserved

 

 

 

 

 

 

(scratch

(scratch

 

 

 

 

 

 

bit)

bit)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bit

 

Descriptions

 

 

 

 

 

 

 

 

 

7:2

Reserved. Read as 000000. Write has no effect.

 

 

 

1Read/Write scratch bit required for VGA compatibility. Read previously written value. Write stores written value.

This bit is a fully readable/writeable MMIO location in the hardware. It has no other functionality in the hardware.

0Read/Write scratch bit required for VGA compatibility. Read previously written value. Write stores written value.

This bit is a fully readable/writeable MMIO location in the hardware. It has no other functionality in the hardware.

Programming Hints :

It has been noted that legacy Video BIOS code has the bits [1:0] programmed to “11” values for reason not fully understood. Experiment was done on 810 Video BIOS with leaving these 2 bits at the default values. It was found that full screen DOS box mode does not behave properly in that case. However, with Video BIOS programming up the bits to “11” values, the problem was corrected.

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Page 85
Image 85
Intel 815 manual 2. SR00Sequencer Reset