Intel G850 CM8062301046204 Data Sheet
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Product codes
CM8062301046204
Datasheet
83
Thermal Specifications and Design Considerations
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.
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.
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 19.
Processor PECI Topology
PECI Host
Controller
Land G5
30
h
Domain 0