Intel CORE 2 DUO E4000 - 3-2008, Техническое описание

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Thermal Specifications and Design Considerations
92 Datasheet
5.4 Platform Environment Control Interface (PECI)
5.4.1 Introduction
PECI offers an interface for thermal monitoring of Intel processor and chipset
components. It uses a single wire, thus alleviating routing congestion issues. Figure 27
shows an example of the PECI topology in a system. PECI uses CRC checking on the
host side to ensure reliable transfers between the host and client devices. Also, data
transfer speeds across the PECI interface are negotiable within a wide range (2 Kbps to
2 Mbps). The PECI interface on the processor is disabled by default and must be
enabled through BIOS.
5.4.1.1 Key Difference with Legacy Diode-Based Thermal Management
Fan speed control solutions based on PECI uses a T
CONTROL
value stored in the
processor IA32_TEMPERATURE_TARGET MSR. The T
CONTROL
MSR uses the same offset
temperature format as PECI though it contains no sign bit. Thermal management
devices should infer the T
CONTROL
value as negative. Thermal management algorithms
should use the relative temperature value delivered over PECI in conjunction with the
T
CONTROL
MSR value to control or optimize fan speeds. Figure 28 shows a conceptual
fan control diagram using PECI temperatures.
The relative temperature value reported over PECI represents the delta below the onset
of thermal control circuit (TCC) activation as indicated by PROCHOT# assertions. As the
temperature approaches TCC activation, the PECI value approaches zero. TCC activates
at a PECI count of zero.
Figure 27. Processor PECI Topology
PECI Host
Controller
Land G5
30
h
Domain 0