Intel Core 2 Duo E7300 BX80570E7300 User Manual

34  

 

Thermal and Mechanical Design Guidelines  

The primary function of the PROCHOT# signal is to provide an external indication that 

the processor has reached the TCC activation temperature. While PROCHOT# is 

asserted, the TCC will be activated. Assertion of the PROCHOT# signal is independent 

of any register settings within the processor. It is asserted any time the processor die 

temperature reaches the trip point.  

PROCHOT# can be configured  using BIOS as an output or bi-directional signal. As an 

output, PROCHOT# will go active when the processor temperature of either core 

reaches the TCC activation temperature. As an input, assertion of PROCHOT# will 

activate the TCC for both cores. The TCC will remain active until the system de-

asserts PROCHOT# 

The temperature at which the PROCHOT# signal goes active is individually calibrated 

during manufacturing. Once configured, the processor temperature at which the 

PROCHOT# signal is asserted is not re-configurable. 

One application of the Bi-directional PROCHOT# is for the thermal protection of 

voltage regulators (VR). System designers can implement a circuit to monitor the VR 

temperature and activate the TCC when the temperature limit of the VR is reached. By 

asserting PROCHOT# (pulled-low) which activates the TCC, the VR can cool down as a 

result of reduced processor power consumption. Bi-directional PROCHOT# can allow 

VR thermal designs to target maximum sustained current instead of maximum 

current. Systems should still provide proper cooling for the VR, and rely on bi-

directional PROCHOT# signal only as a backup in case of system cooling failure.  

Note:  A thermal solution designed to meet the thermal profile specifications should rarely 

experience activation of the TCC as indicated by the PROCHOT# signal going active. 

The Thermal Control Circuit portion of the Thermal Monitor must be enabled for the 

processor to operate within specifications. The Thermal Monitor’s TCC, when active, 

will attempt to lower the processor temperature by reducing the processor power 

consumption. There are two methods by which TCC can reduce processor power 

dissipation. These methods are referred to as Thermal Monitor 1 (TM1) and Thermal 

Monitor 2 (TM2). 

In the original implementation of thermal monitor this is done by changing the duty 

cycle of the internal processor clocks, resulting in a lower effective frequency. When 

active, the TCC turns the processor clocks off and then back on with a predetermined 

duty cycle. The duty cycle is processor specific, and is fixed for a particular processor. 

The maximum time period the clocks are disabled is ~3 s. This time period is 

frequency dependent and higher frequency processors will disable the internal clocks 
for a shorter time period. Figure 

4-1 illustrates the relationship between the internal 

processor clocks and PROCHOT#. 

Performance counter registers, status bits in model specific registers (MSRs), and the 

PROCHOT# output pin are available to monitor the Thermal Monitor behavior.