Platform Environment Control Interface (Peci); Introduction; Key Difference With Legacy Diode-Based Thermal Management; Processor Peci Topology - Intel CORE 2 DUO E4000 - DATASHEET 3-2008 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.
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.
Figure 26.

Processor PECI Topology

PECI Host
Controller
5.4.1.1

Key Difference with Legacy Diode-Based Thermal Management

Fan speed control solutions based on PECI uses a T
processor IA32_TEMPERATURE_TARGET MSR. The T
temperature format as PECI though it contains no sign bit. Thermal management
devices should infer the T
should use the relative temperature value delivered over PECI in conjunction with the
T
CONTROL
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.
90
Land G5
CONTROL
MSR value to control or optimize fan speeds.
Thermal Specifications and Design Considerations
Domain 0
CONTROL
CONTROL
value as negative. Thermal management algorithms
Figure 27
Figure 26
value stored in the
MSR uses the same offset
shows a conceptual
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