82845G Datasheet, PDF (119/193 Pages) Intel Corporation – Intel 82845G/82845GL/82845GV Graphics and Memory Controller Hub (GMCH)

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).
Figure 4-1. Intel^® GMCH Graphics Block Diagram
Instr./
Data
Video Engine
2D Engine
3D Engine
Setup/Tranform
Scan Conversion
Texture Engine
Raster Engine
VGA
Overlay
OCvuersrloary
Primary
Display
Cntl
Alpha
Mux
Blend/
Port
Gamm
/CRC
DDC
DAC
DVOB
DVOC
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.
Intel^® 82845G/82845GL/82845GV GMCH Datasheet
119