Datasheet

Intel
®
82845G/82845GL/82845GV GMCH Datasheet 131
Functional Description
4.5 Display Interfaces
The GMCH has three display ports, one analog and two digital. Each port can transmit data
according to one or more protocols. The digital ports are connected to an external device that
converts one protocol to another. Examples of this are TV encoders, external DACs, LVDS
transmitters, and TMDS transmitters. Each display port has control signals that may be used to
control, configure, and/or determine the capabilities of an external device.
The GMCH has one dedicated display port, the analog port. DVO ports B and C are multiplexed
with the AGP interface. When a system utilizes an AGP connector, DVO ports B and C can be
utilized via an ADD (AGP Digital Display) card. Ports B and C can also operate in dual channel
mode, where the data bus is connected to both display ports, allowing a single device to take data at
twice the pixel rate.
The GMCH’s analog port uses an integrated 350 MHz RAMDAC that can directly drive a standard
progressive scan analog monitor up to a resolution of 2048x1536 pixels with 32-bit color at 60 Hz.
The GMCH’s DVO ports are each capable of driving a 165 MHz pixel clock. Each port is capable
of driving a digital display up to 1600x1200 at 60 Hz. When in dual-channel mode, the GMCH can
drive a flat panel up to 2048x1536 at 60 Hz or dCRT/HDTV up to 1920x1080 at 85 Hz.
The GMCH is compliant with Digital Visual Interface (DVI) Specification, Revision 1.0. When
combined with a DVI compliant external device and connector, the GMCH has a high-speed
interface to a digital display (e.g., flat panel or digital CRT).
NOTE:
1. Single signal software selectable between display enable and Blank#.
Table 4-9. Display Port Characteristics
Interface Protocol Analog Digital Port B Digital Port C
RGB DAC Intel
®
DVO 2.0 DVO 2.0
SIGNALS
HSYNC Yes Enable/Polarity
VSYNC Yes Enable/Polarity
BLANK No Yes
(1)
Yes
(1)
STALL No Yes Yes
Field No Yes Yes
Display_Enable No Yes
(1)
Image Aspect Ratio Programmable and typically 1.33:1 or 1.78:1
Pixel Aspect Ratio Square
(1)
Voltage RGB 0.7 V p-p 1.5 V 1.5 V
Clock NA Differential
Max Rate 350 Mpixel 165/330 Mpixel
Format Analog RGB RGB 8:8:8 YUV 4:4:4
Control Bus DDC1/DDC2B DDC2B
External Device No TMDS/LVDS Transmitter /TV Encoder
Connector VGA/DVI-I DVI/CVBS/S-Video/Component/SCART
Special Functions Monitor Sense Dual Channel Mode