Intel Core™2 Extreme Processor QX6800 (8M Cache, 2.93 GHz, 1066 MHz FSB) HH80562XH0778M Data Sheet
Product codes
HH80562XH0778M
Datasheet
79
Thermal Specifications and Design Considerations
5.3
Platform Environment Control Interface (PECI)
5.3.1
Introduction
PECI offers an interface for thermal monitoring of Intel processor and chipset
components. It uses a single wire, thus alleviating routing congestion issues. 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.
5.3.1.1
Key Difference with Legacy Diode-Based Thermal Management
Fan speed control solutions based on PECI use a T
CONTROL
value stored in the processor
IA32_TEMPERATURE_TARGET MSR. The TCONTROL 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 utilize the relative temperature value delivered over PECI in conjunction with the
TCONTROL 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 16.
Conceptual Fan Control on PECI-Based Platforms
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