Intel Itanium 9140M NE80567KF028009 Manuale Utente

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The Dual-Core Intel Itanium processor 9000 and 9100 series thermal sensing device 
provides a means of acquiring thermal data from the processor. The accuracy of the 
thermal reading is expected to be better than ±5 °C. The thermal sensing device is 
composed of control logic, SMBus interface logic, a precision analog to digital converter, 
and a precision current source. The thermal sensing device drives a small current 
through a thermal diode located on the processor core and measures the voltage 
generated across the thermal diode by the current. With this information, the thermal 
sensing device computes a byte of temperature data. Software running on the 
processor or on a micro-controller can use the temperature data from the thermal 
sensing device to thermally manage the system. 

The thermal sensing device provides a register with a data byte (seven bits plus sign) 
which contains a value corresponding to the sampled output of the thermal diode in the 
processor core. The value of the byte read from the thermal sensor is always higher 
than the actual processor core temperature; therefore, the offset from the reading 
needs to be subtracted to obtain an accurate reading of the processor core 
temperature. This data can be used in conjunction with the upper temperature 
reference byte (provided in the Processor Information ROM) for thermal management 
purposes. The temperature data from the thermal sensor can be read out digitally 
using an SMBus read command (see 

). The thermal sensor detects when 

SMBus power is applied to the processor, and resets itself at power-up. 

The thermal sensing device also contains alarm registers to store thermal reference 
threshold data. These values can be individually programmed on the thermal sensor. If 
the measured temperature equals or exceeds the alarm threshold value, the 
appropriate bit is set in the thermal sensing device status register, which is also 
brought out to the processor system bus via the THRMALERT# signal (see 

 for more details). At power-up, the appropriate alarm register values 

need to be programmed into the thermal sensing device via the SMBus. It is 
recommended that the upper thermal reference threshold byte (provided in the 
processor information ROM) be used for setting the upper threshold value in the alarm 
register. To account for the offset inherent in the thermal sensing device reading, the 
actual programmed value of the upper threshold value in the alarm register should be 
the sum of the upper thermal reference threshold byte and the thermal calibration 
offset byte (both provided in the PIROM).

When polling the thermal sensing device on the processor to read the processor 
temperatures, it is recommended that the polling frequency be every 0.5 to 1 second.

1

7  bits

1

1

8  bits

1

1

7  bits

1

1

8 bits

1

1

1

7  bits

0

1

8  bits

1

8  bits

1

1