Pipeline Performance: 15% Bubbles, 10% 2 Bubbles, 5% 4 Bubbles - ANY HELP?

[juancho]

can anybody help me with this question?


A 10 stage instruction pipeline runs at a clock rate of 1GHz. The data forwarding scheme and the instruction mix are such that for 15% of instructions one bubble, for 10% two bubbles, and for 5% four bubbles must be inserted in the pipelin. The equivalent single-cycle implementation would lead to a clock rate of 150 MHz.

a. what is the reduction in pipeline throughput over the ideal pipeline as a result of bubbles?

b. what is the speedup of the pipelined implementation over the single cycle implementation??

ANY HELP OR POINTERS WILL BE GREATLY APPRECIATED!

 

[vincentm]

What steps have you taken in figuring this out for yourself first? And if you've tried doing so, can you show this work. One of the rules here is that the OP at least show what has been attempted on their part before fishing for solutions to one's HW. In short don't ask for HW help here without doing the work yourself.

 

[quicknote]

I am happy to help you with this question. It seems like you are dealing with a specific type of pipeline performance issue, namely the presence of bubbles. Bubbles are essentially empty or idle stages in the pipeline that occur when an instruction cannot be executed due to a data dependency or other constraint. These bubbles can significantly affect the performance and efficiency of the pipeline.

To answer your first question, the reduction in pipeline throughput due to bubbles can be calculated by taking the percentage of instructions that require bubbles (15% + 10% + 5% = 30%) and multiplying it by the clock rate (1GHz). This gives us a reduction of 300 MHz in pipeline throughput. In other words, the pipeline is only able to process 70% of its maximum capacity due to the presence of bubbles.

To calculate the speedup of the pipelined implementation over the single cycle implementation, we need to compare the clock rates. The single cycle implementation has a clock rate of 150 MHz, while the pipelined implementation has a clock rate of 1GHz. Therefore, the speedup is 1GHz/150 MHz = 6.67x. This means that the pipelined implementation is 6.67 times faster than the single cycle implementation.

In terms of providing pointers, I would suggest looking into techniques such as data forwarding, branch prediction, and out-of-order execution to help reduce the number of bubbles in the pipeline. Additionally, analyzing the instruction mix and identifying any patterns or dependencies can also help optimize the pipeline performance. I hope this helps!