CISC360 Lecture Notes - Lecture 5: Clock Rate, Threshold Voltage, Clock Gating
13 Sep 2016
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Pdynamic ~n * c * v^2 * f * a. A: activity factor (not all transistors may switch this cycle) For a fixed task, reducing clock rate reduces power, not energy. Clock gating disable clocks to unused parts of the chip. Most microprocessors today turn off the clock of inactive modules to save energy and dynamic power. Modern microprocessors typically offer a few clock frequencies and voltages in which to operate that use lower power and energy. Given that pmds and laptops are often idle, memory and storage offer low power modes to save energy. Intel started offering turbo mode in 2008, where chip decides that it"s safe to run at a higher clock rate for a short time possibly on just a few cores until temperature starts to rise. Vt: threshold voltage, voltage at which transistor conducts (begins to switch) Faster algorithms can be converted to lower-power algorithms. Don"t want to wake up the processor every millisecond.
