Average Memory Access Time Calculator
AMAT adds the miss penalty weighted by the miss rate: a 1 ns cache with 95 % hits over 100 ns memory averages 6 ns.
6 ns
- L1 miss rate
- 0.05
- Speedup over memory alone
- 16.66666667
Step-by-step solution
- T = t₁ + (1 − h₁)tₘ
- = 6 ns
- Hierarchical: each level is searched only after a miss in the level above
Average Memory Access Time Formula
AMAT = t₁ + (1 − h₁)[t₂ + (1 − h₂)tₘ]
hierarchical access; simultaneous: h₁t₁ + (1 − h₁)h₂t₂ + …
Worked Example
A 1 ns cache with a 95 % hit rate in front of 100 ns memory:
- T = t₁ + (1 − h₁)tₘ
- = 6 ns
- Hierarchical: each level is searched only after a miss in the level above
Speedup over memory alone: 16.66666667
GATE tip
Read GATE questions carefully for the access model: “the memory is accessed only on a miss” is hierarchical; “all levels are accessed simultaneously” is simultaneous.
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Frequently asked questions
What is the difference between hierarchical and simultaneous access?
Hierarchical (look-through) searches the next level only after a miss, adding its time; simultaneous (look-aside) starts all levels at once, so a miss costs only the lower level’s time.
What is a local versus global miss rate?
The local L2 miss rate counts misses among L2 accesses; the global rate counts them among all accesses: global = (1 − h₁)(1 − h₂).
Sources
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Average Memory Access Time Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/amat-calculator/
IEEE
Scientific Converters, "Average Memory Access Time Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/amat-calculator/