Intel G640T BX80623G640T Data Sheet

Datasheet

83

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. 

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. 

PECI Host 

Controller

Land G5

30

h

Domain 0