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In a CPU with L1, L2 and L3 caches, which level is smallest and fastest?

L1, the level closest to the processor core.

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  1. L3
  2. L2
  3. L1 ✔

Why: A small cache can be very fast, but it misses more often. So chips stack levels: a tiny, quick L1, then a bigger L2, then a larger L3. A miss in one level checks the next before going out to slow main memory.

Huh, didn't know that: Most processors today have up to three levels of cache between the core and RAM.

The dad joke
Why is L1 cache always first in line? It's the closest friend the CPU has.
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References

Answer: L1. A small cache can be very fast, but it misses more often. So chips stack levels: a tiny, quick L1, then a bigger L2, then a larger L3. A miss in one level checks the next before going out to slow main memory.

  1. OpenStax Introduction to Computer Science 5.5: Memory Hierarchy openstax.org/books/introduction-computer-science/pages/5-5-memory-hierarchy
    Level 1 (L1), closest to the processor, is small in capacity and very fast but with a potentially low hit rate.
    Checked 2026-10-10.

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