
Intel
82815EM GMCH
R
146
Datasheet
4.14.
System Clock Description
4.14.1.
External Clock Sources
The GMCH2-M device shall receive the following clock frequencies and references:
100/66 MHz host clock, used to run core logic (host, 2D, 3D).
66 MHz AGP/Hub Interface.
48 MHz reference - used to derive video dot clocks for Display and LCD/TVOut interfaces.
40 MHz Tvclkin from the External DVO device
The following table describes the clock alignments for the external clock sources.
Table 23. Supported Frequencies and Corresponding Phase Alignments
Host
Interface
(HCLK)
Hub / AGP
Interface
(BCLK)
System
Memory
(SCLK)
Local
Memory
(LCLK)
Core
(RCLK)
External Phase
Alignment
100 Mhz
66 Mhz
66 Mhz
100 Mhz
133Mhz
100 Mhz
HCLK and BCLK 180
degrees out of phase
100 Mhz
100 Mhz
66 Mhz
100 Mhz
133Mhz
100 Mhz
HCLK and SCLK 180
degrees out of phase
4.14.2.
Internal Clock Sources
The internal graphics device shall source the following interface frequencies and references:
1. 100 MHz for the system memory subsystem.
2. 133/100 MHz for the local memory subsystem.
3. 100 MHz for the graphics core.
4. 266/133/66 MHz for AGP in 4X/2X/1X modes respectively.
5. 66 MHz for the hub interface.
6. 20-112 MHz – LCD/TVout interface.
4.15.
Power Management