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164
Intel
82865G/82865GV GMCH Datasheet
Functional Description
5.4
Integrated Graphics Controller
The GMCH provides a highly integrated graphics accelerator and chipset while allowing a flexible
integrated system graphics solution.
High bandwidth access to data is provided through the graphics and system memory ports. The
GMCH can access graphics data located in system memory at 2.1 GB/s – 6.4 GB/s (depending on
memory configuration). 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 @ 75Hz. The DVO ports are capable of driving a variety
of TV-Out, TMDS, and LVDS transmitters.
As seen in
Figure 13
, the Internal Graphics Device contains several types of components. The
major components in the IGD are the engines, planes, pipes and ports. The GMCH has a 3D/2D
Instruction Processing unit to control the 3D and 2D engines. The IGD’s 2D and 3D engines are fed
with data through the memory controller. The output of the engines are surfaces sent to memory,
which are then retrieved and processed by the GMCH’s planes.
The GMCH contains a variety of planes, such as display, overlay, cursor, and VGA. A plane
consists of rectangular shaped image that has characteristics such as source, size, position, method,
and format. These planes get attached to source surfaces, which are rectangular memory surfaces
with a similar set of characteristics. They are also associated with a particular 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 only 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
Section 5.5
.
The entire IGD is fed with data from its memory controller. The GMCH’s graphics performance is
directly related to the amount of bandwidth available. If the engines are not receiving data fast
enough from the memory controller (e.g., single-channel DDR266), the rest of the IGD will also be
affected.
Figure 13. GMCH Graphics Block Diagram
Instr./
Data
Video Engine
2D Engine
Setup/Transform
3D Engine
Scan Conversion
Texture Conversion
Raster Engine
VGA
Primary
Display
Overlay
Cursor
Alpha
Blend /
Gamma /
CRC
Cntl
Mux
Port
DDC
DAC
DVOB
DVOC