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

Frequency
1 10 100 1000
PhaseLength(ms)
3D Productivity
E-learning VideoCreation
Figure 4.8 Core Power Phase Duration
This is further supported by Figure 4.9, which group the most common phases by
combinations of amplitude and duration. Note that all phases less than 10 ms are
considered to be 10 ms. This simplifies presentation of results and is reasonable since the
OS does not apply adaptation changes any faster than 10 ms. These figures show that the
highest power phases only endure for a short time. These phases, which are present only
in 3D and – to a much lesser degree – in video creation, are only possible when multiple
cores are active. The lack of long duration high power phases is attributable to two
causes: low percent of multithreaded phases and higher IPC dependence during
multithreaded phases. The dependence on IPC for phase length increases as the number
of active cores increases. When many cores are active the power differences are caused
by changes in active power due to IPC (performance). When few cores are active, total
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