Hub Datasheet

Intel
®
E7505 Chipset MCH Datasheet 171
Functional Description
5.7.3 Clock Control
The clocks in the platform fall into three categories:
• The first category consists of those clocks that turn on and off during normal operation
(e.g., a serial port clock).
• The second category consists of clocks that never turn off. Only the 32.768 kHz RTC clock
falls into this category.
• The third category consists of those clocks that must be active in normal operation but are
actively controlled by the platform to manage power.
The platform separates the third category into two groups: the host clock group and the I/O clock
group. All of the clocks in a group are controlled as a set (i.e., turning on and off together).
ACPI Clock Summary
The mapping between the ACPI states and the states of the system clocks is shown in Table 5-11.
Note that the ten ACPI states only map to four distinct states of the system clocks. In both the G0/
S0/C0 and G0/S0/C1 states all system clocks are on. Some clocks internal to the processor may be
shut down in G0/S0/C1 as a result of the processor executing an auto-halt.
In G1/S3 through G2/S5 states all system clocks except for the RTC clock have been shutdown.
The RTC clock is used to detect wake events when the system is in any of these states. The G3 state
is hard off with the power supply mechanically isolated.
The ACPI C-states refer to processor states. Since the MCH is closely coupled to the processor, the
MCH’s various power states defined in this document are also called C-states.
5.8 Clocking
The MCH is supported by the CK408 compliant clock synthesizer. For details, refer to the Intel
®
Xeon™ Processor and Intel
®
E7505 Chipset Platform Design Guide and the CK408 Clock
Synthesizer/Driver Specification.
5.9 System Reset and Power Sequencing
For details, refer to the Intel
®
Xeon™ Processor and Intel
®
E7505 Chipset Platform Design Guide.
Table 5-11. ACPI State to Clock State Mapping
G State S State C State
Processor
State
Processor
Clock
MCH
Clock
DRAM Clock
PCI
Clock
G0 S0 C0 Full On On On On On
G0 S0 C1 Auto-Halt On On On On
G1 S1 N/A C2 ON ON ON ON
G1 S3 N/A N/A Off Off Off Off
G1 S4 N/A N/A Off Off Off Off
G2 S5 N/A N/A Off Off Off Off
G3 N/A N/A N/A Off Off Off Off