Intel E5-4600, E5-2600 manual Temperature Filtering, Reserved Values, Error Codes and Descriptions

Temperature readings from the processor are always negative in a 2’s complement format, and imply an offset from the processor Tjmax (PECI = 0). For example, if the processor Tjmax is 100°C, a PECI thermal reading of -10 implies that the processor is running at approximately 10°C below Tjmax or at 90°C. PECI temperature readings are not reliable at temperatures above Tjmax 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 centigrade. A change of ‘1’ in the PECI count represents roughly a temperature change of 1 degree centigrade. 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.

2.5.7.3Temperature Filtering

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:

TN = (1-α)* TN-1+ α * TSAMPLE

where TN and TN-1are the current and previous averaged PECI temperature values respectively, TSAMPLE 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 Section 2.5.2.6.21.

2.5.7.4Reserved Values

Several values well out of the operational range are reserved to signal temperature sensor errors. These are summarized in Table 2-24.

Table 2-24. Error Codes and Descriptions

Error Code	Description
0x8000	General Sensor Error (GSE)
0x8001	Reserved
0x8002	Sensor is operational, but has detected a temperature below its operational range
	(underflow)
0x8003-0x81ff	Reserved

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Intel® Xeon® Processor E5-1600/E5-2600/E5-4600 Product Families	77
Datasheet Volume One