Question

Consider that you have a code of 500,000 instructions which is executed using a 14 stages pipeline. it is expected that 10% of the instructions will cause an exception. in order to handle the exception, there is an exception handler which is using 40 cycles to execute (includes the flushing and reloading and the actual handling of the exception). the pipeline frequency is 4 ghz.

how many cycles does it take to execute the code?

Answer 1

To execute the code with 500,000 instructions on a 14-stage pipeline at 4 GHz, taking into account a 10% exception rate with each exception handler using 40 cycles, it would take a total of 2,500,013 cycles.

Step-by-step explanation:

To calculate the number of cycles it takes to execute a code of 500,000 instructions on a 14 stages pipeline with a frequency of 4 GHz, we must first consider the time it takes for each instruction to pass through the pipeline, as well as the additional cycles used by the exception handler.

Without exceptions, a 14-stage pipeline would take at least 14 cycles to get the first instruction out, and then 1 cycle for each subsequent instruction, since they are pipelined. So theoretically, if there were no penalties for exceptions or other pipeline stalls, it would take 500,000 + 13 cycles (500,013 cycles) to execute the entire code.

However, 10% of the instructions are expected to cause an exception, each taking an extra 40 cycles. This means 50,000 instructions each will add 40 cycles, totaling an additional 2,000,000 cycles (50,000 instructions * 40 cycles/instruction) for exception handling.

The total number of cycles to execute the code, including exception handling, would be 500,013 (initial cycles to fill and empty the pipeline) + 2,000,000 (exception handling cycles) = 2,500,013 cycles.