Intel QX6700 HH80562PH0678M User Manual

80

Datasheet

PECI offers an interface for thermal monitoring of Intel processor and chipset 

components. It uses a single wire; thus, alleviating routing congestion issues. 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 use 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. 

.

Min

Max

Fan Speed

(RPM)

T

CONTROL

Setting

TCC Activation 

Temperature

PECI = 0 

PECI = -10 

PECI = -20 

Temperature

Note: Not intended to depict actual implementation