Intel C2518 FH8065501516710 Data Sheet

Intel

®

 Atom™ Processor C2000 Product Family for Microserver

September 2014

Datasheet, Vol. 2 of 3

Order Number: 330061-002US

427

When accessed using the PECI GetTemp() command, the temperature is formatted in a 

16-bit, 2s complement value representing a number of 1/64  °C. See 

. 

This format allows temperatures in a range of +/-512 °C to be reported to 

approximately a 0.016 °C resolution.

The resolution of the processor Digital Thermal Sensor (DTS) is approximately 1 °C, 

which can be confirmed by a performing a Read Model-Specific Register (RDMSR) 

Intel

®

 architecture instruction to the IA32_THERM_STATUS MSR (19Ch)where it is 

architecturally defined. Note that the MSR read will return only bits [13:6] of the PECI 

temperature sensor data defined in 

. PECI temperatures are 

sent through a configurable low-pass filter prior to delivery in the GetTemp() response 

data. The output of this filter produces temperatures at the full 1/64 °C resolution even 

though the DTS itself is not this accurate.

Temperature readings from the processor are always negative in a 2s complement 

format, and imply an offset from the processor T

J

-

MAX

 (PECI = 0). For example, if the 

processor T

J

-

MAX

 is 100 °C, a PECI thermal reading of -10 implies that the processor is 

running at approximately 10 °C below T

J

-

MAX

 which would be 90 °C. PECI temperature 

readings are not reliable at temperatures above T

J

-

MAX

 since the processor is outside its 

operating range and hence, PECI temperature readings are never positive.

The changes in PECI data counts are approximately linear in relation to changes in 

temperature in degrees Celsius. A change of 1 in the PECI count represents roughly a 

temperature change of 1 °C. This linearity is approximate and cannot be guaranteed 

over the entire range of PECI temperatures, especially as the offset from the maximum 

PECI temperature (zero) increases.

The processor Digital Thermal Sensor (DTS) provides an improved capability to monitor 

device hot spots, which inherently leads to more varying temperature readings over 

short time intervals. Coupled with the fact that typical fan speed controllers may only 

read temperatures at 4Hz, it is necessary for the thermal readings to reflect thermal 

trends and not instantaneous readings. Therefore, PECI supports a configurable low-

pass temperature filtering function that is expressed by the equation:

T

N

 = (1-α) * T

N-1

 + α * T

SAMPLE

where T

N

 and T

N-1

 are the current and previous averaged PECI temperature 

values respectively, T

SAMPLE

 is the current PECI temperature sample value and 

the variable ‘α’ = 1/2X, where X is the Thermal Averaging Constant that is 

programmable as described in 

.

Fractional 

Value

(approx 0.016)

15 14

6 5

0

Integer Value

(0-511 decimal)

Sign

S