$(5$ marks$)$ Performance

ume multiply instruction takes $12$ cycles and accounts for $15\%$ of the instructions in a typical gram, whereas the other $85\%$ of the instructions require an average of $4$ cycles for each instruction.

a$)$ What percentage of time does the CPU spend doing multiplication? $(3$ marks$)$

b$)$ If the number of cycles taken by multiplication could be reduced to $8$ on the expense of increasing the cycle time by $20\%,$ should we go for it$?(2$ marks$)$