Our favorite program runs in 10 seconds on computer a, which has a 2 ghz clock. we are trying to a computer designer build a computer, b, which will run this program in 6 seconds. the designer has determined that a substantial increase in the clock rate is possible, but this increase will affect the rest of the cpu design, causing computer b to require 1.2 times as many clock cycles as computer a for this program. what clock rate should we tell the designer to target?

4 GHz

Explanation:

Time taken for computer A to execute the program is = 10 secs

Given frequency of the clock for computer A is = 2 GHz

We know Clock period = 1 / frequency = 1 / 2 * 109 = 0.5 ns

Number of clocks requried to execute the program in computer A is

= Total Execution time / clock period = 10 / 0.5 * 10-9 = 20 * 109 clocks

Given Time taken for computer B to execute the program is = 6 secs

Given computer B requries 1.2 times as many clocks as computer A

implies number of clocks to execute program in computer B = 1.2 * 20 * 109 = 24 * 109

Here clock period of computer B = Total execution time / number of clocks

                               = 6 secs / 24 * 109

                               = 0.25 ns

Hence clock rate = frequency is = 1 / clock period = 1 / 0.25 ns = 4 GHz.

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