$*($Important$)**$The red part is the correct answer. Please refer to the correct answer in red and explain the process of solving this problem one by one in detail$*$Look at the following MIPS code and answer the question.

$8-1.(10$ points$)$ Show the command execution action in the multi$-$cycle pipeline diagram below. Mark step $5$ IFID,EX$,$M$,$W$,$ and bubble as X$.$ However, there is no forwarding unit.

$\backslash$table$[[,$O$1,02,03,04,05,06,07,08,09,10,11,12,13,14,15,16,17,18],[$I$1$: ADD,IF$,$ID$,$EX$,$M$,$W$,,,,,,,,,,,,,],[$I$2$: SUB,,IF$,$X$,$X$,$ID$,$EX$,$M$,$W$,,,,,,,,,,],[$I$3$: ADD,,,,,IF$,$ID$,$EX$,$M$,$W$,,,,,,,,,]]$

$8-2.(10$ points$)$ Add the forwarding unit, repeat question $8-1.$

$\backslash$table$[[,01,02,03,04,05,06,07,08,09,10,11,121,13,14,15,16,17,18],[$I$1$: ADD,If$,$ID$,$EX$,$M$,$w$,,,,,,,,,,,,,],[12$: SUB,,IF$,$ID$,$EX$,$M$,$w$,,,,,,,,,,,,],[13$: ADD,,,If$,$ID$,$EX$,$M$,$W$,,,,,,,,,,,],[14$: LW$,,,,$IF$,$ID$,$EX$,$M$,$W$,,,,,,,,,,],[$IS: LW$,,,,,$If$,$X$,10,$EX$,$M$,$W$,,,,,,,,],[16$: SW$,,,,,,,$IF$,$ID$,$EX$,$M$,$w$,,,,,,,],[17$: AND,,,,,,,,IF$,1$D$,$EX$,$M$,$w$,,,,,,]]$

$8-3.(10$ points$)$ Average CPI is defined as the average cycle taken to process one command, and is obtained by dividing "the total number of cycles taken to process all commands" by the total number of commands. Find the average CPI for each of the two cases and find how many times the performance has improved by adding the forwarding unit.

Answer:

$17/12.$