Frequency/Vid Control - Intel BX80613I7980 Datasheet

6.2.2.1

Frequency/VID Control

When the Digital Temperature Sensor (DTS) reaches a value of 0 (DTS temperatures
reported using PECI may not equal zero when PROCHOT# is activated, see
for further details), the TCC will be activated and the PROCHOT# signal will be
asserted. This indicates the processor temperature has met or exceeded the factory
calibrated trip temperature and it will take action to reduce the temperature.
Upon activation of the TCC, the processor will stop the core clocks, reduce the core
ratio multiplier by 1 ratio and restart the clocks. All processor activity stops during this
frequency transition, which occurs within 2 us. Once the clocks have been restarted at
the new lower frequency, processor activity resumes while the voltage requested by the
VID lines is stepped down to the minimum possible for the particular frequency.
Running the processor at the lower frequency and voltage will reduce power
consumption and should allow the processor to cool off. If after 1 ms the processor is
still too hot (the temperature has not dropped below the TCC activation point, DTS
still = 0 and PROCHOT is still active), then a second frequency and voltage transition
will take place. This sequence of temperature checking and Frequency/VID reduction
will continue until either the minimum frequency has been reached or the processor
temperature has dropped below the TCC activation point.
If the processor temperature remains above the TCC activation point even after the
minimum frequency has been reached, then clock modulation (described below) at that
minimum frequency will be initiated.
There is no end user software or hardware mechanism to initiate this automated TCC
activation behavior.
A small amount of hysteresis has been included to prevent rapid active/inactive
transitions of the TCC when the processor temperature is near the TCC activation
temperature. Once the temperature has dropped below the trip temperature, and the
hysteresis timer has expired, the operating frequency and voltage transition back to
the normal system operating point using the intermediate VID/frequency points.
Transition of the VID code will occur first, to insure proper operation as the frequency is
increased. Refer to
Figure 6-4. Frequency and Voltage Ordering
VIDf VIDf
VIDf VIDf
VIDf VIDf
82
Table 6-4 for an illustration of this ordering.
f f
MAX MAX
f f
1 1
f f
2 2
MAX MAX
1 1
2 2
Temperature Temperature
Frequency Frequency
VID VID
PROCHOT# PROCHOT#
Thermal Specifications
Section 6.3
Datasheet, Volume 1