Copyright by William Lloyd Bircher 2010 - The Laboratory for ...

Core Power (Watts)
60
50
40
30
20
10
Leakage
Dynamic
0
35 50 65
Die Temperature (Celsius)
80 95
Figure 3.2 Temperature Sensitivity of Leakage Power
As expected, a linear change in frequency yields a linear change in power consumption.
However, linear changes in temperature yield exponential changes in power
consumption. Note that static power is identified by the Y-intercept in the chart. This is
a critical observation since static power consumption represents a large portion of total
power at high temperatures. Therefore, an effective power management scheme must
also scale voltage to reduce the significant leakage component. To see the effect of
voltage scaling consider Figure 3.3.
Leakage power
varies exponentially
with temperature
Dynamic power
constant for fixed
voltage and frequency
Figure 3.3 shows the cumulative effect of p-states and c-states. Combinations of five p-
states (x-axis) and four operating modes are shown. The lowest power case, C1e-Idle,
represents all cores being idle for long enough that the processor remains in the C1e state
more than 90 percent of the time. The actual amount of time spent in this state is heavily
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