ITPEC IP April 2025 Question 11

Primary cache first, then secondary cache on a miss — the CPU searches the cache levels from the fastest to the slowest.

The memory hierarchy runs from the CPU outward: primary cache (L1), secondary cache (L2), main memory. Each level is larger but slower than the one before. On a read, the CPU looks in the primary cache; if the data is not there it tries the secondary cache, and only if that also misses does it read main memory, copying the data into the caches on the way.

Answer (c)

Why not others:

• •(a) — it is the other way round: the primary cache is the smallest and fastest level, the secondary cache is larger
• •(b) — every cache level is faster than main memory; a secondary cache slower than main memory would be pointless
• •(d) — a program's data sits in main memory; the caches fill on demand with copies of the data as it is used, and could not hold everything anyway

Key rule: Memory levels trade capacity for speed: the closer to the CPU, the smaller and faster, and a read goes down the levels only when the level above misses.

Computer Component · AI-written, may contain errors