Branch Misprediction Penalty Calculator
Work out branch misprediction penalty instantly with clear inputs, formula shown and shareable results.
About Branch Misprediction Penalty Calculator
A misprediction flushes the pipeline, so the penalty is roughly the pipeline depth in cycles — and on a wide machine that means depth times issue width of lost instruction slots. With 18% branches at 3% misprediction, a 19-stage pipeline loses meaningful performance.
Formula
Mispredict cost
CPI added = branch frequency x mispredict rate x pipeline depth
Worked example
With the default values below, Branch Misprediction Penalty Calculator returns CPI added by mispredicts of 0.1026. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Pipeline depth
- 19 stages
- Misprediction rate
- 3 %
- Branch frequency
- 18 %
- Base IPC
- 3 IPC
Results
- CPI added by mispredicts
- 0.1026 cycles
- Penalty per mispredict
- 19 cycles
- Performance loss
- 23.536% %
- Mispredicts per 1000 instructions
- 5.40
Step by step
- 1Values used
- 2Mispredict cost
- 3CPI added by mispredicts= 0.1026 cycles
- 4Penalty per mispredict= 19 cycles
- 5Performance loss= 23.536 %
- 6Mispredicts per 1000 instructions= 5.40
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or fees or charges into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why do wide pipelines suffer more?
Each flushed cycle discards issue-width instruction slots, so a 4-wide 20-stage machine loses up to 80 instruction slots per mispredict.
How accurate are modern predictors?
TAGE-class predictors reach 98-99% on typical code, but hard-to-predict data-dependent branches remain the main limit on single-thread performance.
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