3. Power and Performance II [20 marks] A fully parallelizable program has 60,000

Question

3. Power and Performance II [20 marks]

A fully parallelizable program has 60,000 operations (ops). A multicore die

has four hot cores. Each hot core dissipates 120 W and performs 2 ops/ns.

The die also has 40 cool cores. Each cool core dissipates 50 W and performs

1 op/ns.

a) Calculate the execution time and energy consumed if the program is run on

the four hot cores and the 40 cool cores are turned off.

b) Calculate the execution time and energy consumed if the program is run on

the 40 cool cores and the four hot cores are turned off.

Explanation / Answer

so by using four hot cores:
   ops per ns: 4*2 = 8
   operation time = 60000/8 ns = 7500ns
   Energy dissipated= 120 * 4 * 7.5e-6 = 0.0036 Joule

so by using 40 cool cores:
   ops per ns: 40*1 = 40
   operation time: 60000/40 = 1500ns
   Energy dissipated= 50 * 40 * 1.5e-6 = 0.003 Joule

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