845GL datasheet(119/193 Pages) INTEL

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

119

Functional Description

4.4

Integrated Graphics Device (IGD)

The GMCH provides a highly integrated graphics accelerator while allowing a flexible integrated

system graphics solution (see Figure 4-1).

High-bandwidth access to data is provided through the system memory port. The GMCH can

access graphics data located in system memory at 1.0 GB/s (using SDR, PC133 memory),

1.6 GB/s (using DDR200 memory), and 2.1 GB/s (using DDR266). The GMCH uses Intel’s Direct

Memory Execution model to fetch textures from system memory. The GMCH includes a cache

controller to avoid frequent memory fetches of recently used texture data.

The GMCH is able to drive an integrated DAC, and/or two DVO ports (multiplexed with AGP)

capable of driving an ADD card. The DAC is capable of driving a standard progressive scan analog

monitor with resolutions up to 2048x1536 at 60 Hz. The DVO ports are capable of driving a variety

of TV-Out, TMDS, and LVDS transmitters.

The GMCH’s IGD contains several functional units (see Figure 4-1). The major components in the

IGD are the graphics engines, planes, pipe, and ports. The GMCH has a 3D/2D Instruction

Processing unit to control the 3D and 2D engines. Data is input to the IGD’s 2D and 3D engines

from the system memory controller. The output of the engines are surfaces sent to memory, which

are then retrieved and processed by GMCH’s planes.

The GMCH contains a variety of planes (e.g., primary display, overlay, cursor, and VGA). The

IGD does not support VGA memory accesses during graphics accelerator operations (e.g., 2D and

3D engine activity). The Intel graphics driver controls VGA and high-resolution graphics

interaction. VGA and high resolution interaction will remain exclusive.

A plane consists of a rectangular shaped image that has characteristics such as source, size,

position, method, and format. These planes get attached to source surfaces that are rectangular

memory surfaces with a similar set of characteristics. They are also associated with a destination

pipe.

A pipe consists of a set of combined planes and a timing generator. The GMCH has a single display

pipe, which means that the GMCH can support a single display stream. A port is the destination for

the result of the pipe. The GMCH contains three display ports, 1 analog (DAC), and two digital

(DVO ports B and C). The ports will be explained in more detail in a subsequent section.

Figure 4-1. Intel® GMCH Graphics Block Diagram

Instr./

Data

3D Engine

Setup/Tranform

Scan Conversion

Texture Engine

Raster Engine

2D Engine

Primary

Display

Alpha

Blend/

Gamm

/CRC

Cntl

Mux

Port

DAC

DVOC

DVOB

DDC

Overlay

VGA

Overlay

Cursor

Video Engine

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