845GL datasheet(127/193 Pages) INTEL

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Intel® 82845G/82845GL/82845GV GMCH Datasheet

127

Functional Description

4.4.1.7

GMCH VGA Registers

The 2D registers are a combination of registers defined by IBM when the Video Graphics Array

(VGA) was first introduced and others that Intel has added to support graphics modes that have

color depths, resolutions, and hardware acceleration features that go beyond the original VGA

standard.

4.4.1.8

Logical 128-Bit Fixed BLT and 256-Bit Fill Engine

Using this BLT engine accelerates the Graphical User Interface (GUI) of Microsoft Windows*.

The 128-bit GMCH BLT Engine provides hardware acceleration of block transfers of pixel data for

many common Windows operations. The term BLT refers to a block transfer of pixel data between

memory locations. The BLT engine can be used for the following:

• Move rectangular blocks of data between memory locations.

• Data Alignment.

• Perform logical operations (raster ops).

The GMCH BLT engine has the ability to expand monochrome data into a color depth of 8, 16, or

32 bits. BLTs can be either opaque or transparent. Opaque transfers, move the data specified to the

destination. Transparent transfers, compare destination color to source color and write according to

the mode of transparency selected.

Data is horizontally and vertically aligned at the destination. If the destination for the BLT overlaps

with the source memory location, the GMCH can specify which area in memory to begin the BLT

transfer. Hardware is included for all 256 raster operations (Source, Pattern, and Destination)

defined by Microsoft, including transparent BLT.

The GMCH has instructions to invoke BLT and STRBLT operations, permitting software to set up

instruction buffers and use batch processing. The GMCH can perform hardware clipping during

BLTs.

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