問65
頻出度★★☆
CPU に搭載された1次と2次のキャッシュメモリに関する記述のうち, 適切なものはどれか。
平成30年度 秋期 ITパスポート試験 問65
テクノロジ系コンピュータ構成要素 › メモリ
This question's explanation and your answers so far.
解説
問 65
Incorrectア
It is the opposite. The L1 cache is the fastest but has a small capacity, while the L2 cache has a larger capacity. In other words, in speed L1 > L2, and in capacity L1 < L2.
Incorrectイ
Cache memory is placed precisely to be faster than main memory, so even the L2 cache reads and writes faster than main memory. The statement “slower than main memory” is wrong.
- ウ
正解 Cache memory is a high-speed buffer placed to bridge the speed gap between the CPU and main memory, and it is layered from nearest to the CPU as “L1 (level 1) → L2 (level 2) → main memory”. When the CPU reads data, it first searches the fastest L1 cache; if the data is not there, it accesses the next-fastest L2 cache; and if it is still not found, it accesses main memory. Choice “ウ” correctly describes this reference order, so it is appropriate.
Incorrectエ
The data needed for processing is stored in main memory and is loaded into the cache when the CPU needs it. There is no constraint that all data must reside in the cache at the start (besides, the cache has a small capacity and cannot hold all the data).
ここがポイント
- Memory hierarchy: the closer to the CPU, the faster and the smaller the capacity; access proceeds in the order register → L1 cache → L2 cache → main memory, and when an upper level misses, the next lower level is referenced.
- The purpose of cache memory is to bridge the speed gap between the CPU and main memory, so every cache level is faster than main memory.
用語