What is Cycles per instruction (CPI)?

The average number of clock cycles per instruction, one factor in execution time = instruction count × CPI × cycle time, and the reciprocal of IPC.

Field: Performance Analysis

Cycles per instruction (CPI) in the explanations

Questions that mention Cycles per instruction (CPI) (9)

  1. Approximately how many instructions per second can a processor with a 2 GHz clock and an average CPI (clocks per instruction) of 0.5 execute?
  2. A processor has an average CPI of 1.0 with a perfect cache. Each instruction makes 1.3 memory accesses on average, with a 2% miss rate and a 100-cycle miss penalty. What is the actual average CPI?
  3. A program executing 1 billion instructions runs on a CPU with average CPI 2 and clock frequency 2 GHz. What is the execution time?
  4. A CPU design change raises clock frequency 1.5× but also raises CPI 1.2× (instruction count unchanged). How many times faster is execution?
  5. A new compiler optimization reduces executed instructions by 20% but increases average CPI by 10% (frequency unchanged). What is its effect?
  6. A program's instruction mix is 50% integer ALU (CPI 1), 30% loads and stores (CPI 2) and 20% branches (CPI 5). What is the average CPI?
  7. Which metric indicates the number of instructions executed per clock?
  8. In chips using mechanically weak low-k films, what is the problem called in which stress during packaging cracks or delaminates the films?
  9. Which is the basic formula for a program's CPU execution time?

Related terms

Superscalar Miss penalty Speedup IPC Out-of-order execution Branch prediction Instruction set architecture (ISA) Benchmark CPU time Flame graph

Back to the glossary