The figure below illustrates a system in which operations occur as three consecu

Question

The figure below illustrates a system in which operations occur as three consecutive clock cycles. Actions taking place in clock cycle 1 are scalable: that is, if the clock cycle time changes, the actions can be speeded up or slowed down correspondingly. In cycle 2, the action process I requires 25 ns and in clock cycle 3 the action process 2 requires 32 ns. If the clock cycle is less than the time required for process 1 or process 2, then one or more wait cycles have to be inserted for the process to complete. 2. Cycle 1 Cycle 2 Cycle 3 Clock Process 1 Process2 25 ns 32 ns What is the time to complete an operation if the clock cycle time is a, 40 ns b. 30 ns c. 10 ns [3 marks]

Explanation / Answer

a) Clock Cycle Time is 40 ns.

Both process 1 and process 2 are below 40 ns , so there is no need of additional cycles, so the whole process will be completed in 3 clock cycles, without the need of any additional cycles. Thus it will be 3 * 40 = 120 ns

b) Clock Cycle Time is 30 ns

Process 1 is less than 30 ns, so it will be completed in the first run.

But Process 2 is longer than 30 ns, so it will be continued on to the second run and will be finished in the second run as 32 ns can be covered in 2 * 30 = 60 ns

Thus the total number of Cycles will be 2 * 3 = 6 Clock cycles which is 6 * 30 = 180 ns

c) Clock Cycle Time is 10 ns

It is less than both Process 1 and Process 2.

It will take 3 runs for Process 1 as 25 ns is less than 3 * 10 ns.

It will take 4 runs for Process 2 as 32 ns is less than 4 * 10 ns

Thus side by side, both the processes will be over by the fourth run

Thus it will take 4 runs which is 4 * 3 * 10 = 120 ns

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