4 [20/10/20] <1.5> Figure 1.23 presents the power consumption of several compute

Question

4 [20/10/20] <1.5> Figure 1.23 presents the power consumption of several computer system components. In this exercise, we will explore how the hard drive affects power consumption for the system. a. [20] <1.5> Assuming the maximum load for each component, and a power supply efficiency of 80%, what wattage must the server’s power supply deliver to a system with an Intel Pentium 4 chip, 2 GB 240-pin Kingston DRAM, and one 7200 rpm hard drive? b. [10] <1.5> How much power will the 7200 rpm disk drive consume if it is idle roughly 60% of the time? c. [20] <1.5> Given that the time to read data off a 7200 rpm disk drive will be roughly 75% of a 5400 rpm disk, at what idle time of the 7200 rpm disk will the power consumption be equal, on average, for the two disks?

Explanation / Answer

a.

Peak Power Consumption          = 1* 66 + 4 * 2.3 + 1 * 7.9

                                                      = 66.0 + 9.2 + 7.9

                                                      = 83.1 W

Power Supply Wattage   = 83.1 / 0.8

                                          = 103.9 W

b.

Let the 7200-disk busy time = x

7200-disk power              = 5400-disk power

4.0 * (1-x) + 7.9 * x          = 2.9 * (1-x/0.75) + 7.0 * x/0.75

4.0 + 3.9 x                         = 2.9 – 3.87 x + 9.33 x

1.1                                     = 5.47 x – 3.9 x

Hence x = 0.70                       

Idle time = 1.0 – 0.70 = 0.30

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