Pipeline Calculations: how many clock ticks will it take to execute a sequence of instructions?

Let's say that there are 1234 instructions in the sequence and 5 ticks per instruction.

If there is no pipeline, we multiply:

The number of clock ticks for a sequence of instructions is the product of the number of ticks per instruction and the number of instructions in the sequence

The number of ticks for our example sequence would then be 5 * 1234 = 6170

If there is a pipeline, we add:

The number of clock ticks for a sequence of instructions is the sum of the number of ticks per instruction and the number of instructions in the sequence minus 1

How do we know that?

• The number of ticks to get the first instruction done is just the number of ticks per instruction.
• Once that is done, the number of instructions left to do is one less than the number of instructions in the sequence.
• Once the first instruction completes, another instruction completes in each following tick.

The number of ticks for our example sequence would then be 5 + 1233 = 1238

Compare 6170 to 1238 to get an idea of the speedup we get from pipelining.