Components of the CPI
CPI for single instruction issue with ideal pipeline = 1
Previous formula can be expanded to take into account classes of instructions
- For example in RISC machines: branches, f.p., load-store.
- For example in CISC machines: string instructions
CPI = ? CPIi * fi where fi is the frequency of instructions in class i
Will talk about “contributions to the CPI” from, e.g,:
- memory hierarchy
- branch (misprediction)
- hazards etc.