問92
頻出度★★☆
CPUのキャッシュメモリに関する説明のうち, 適切なものはどれか。
平成29年度 春期 ITパスポート試験 問92
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 92
Incorrectア
This is the opposite. Because cache memory is fast it is expensive, so its capacity is made small, much smaller than the main memory. There is neither a need nor a reason to make it as large as the main memory or larger.
- イ
正解 Cache memory is a high-speed but small-capacity storage device placed between the CPU and the main memory. If frequently used data and instructions are kept here, the CPU does not have to access the slower main memory every time, and when there is a hit it can obtain the data in a shorter time. As a result, the averaged time of accesses to the main memory (the effective access time) becomes shorter. Therefore choice イ, which says it is used to shorten the effective access time of the main memory, is appropriate.
Incorrectウ
Whether the cache works is determined not by the capacity of the main memory but by locality of reference, that is, using the same data repeatedly. The cache is effective even on a computer with a large main memory, so saying it has no effect is wrong.
Incorrectエ
Storing into and replacing data in the cache is done automatically by the hardware and is invisible to the user (transparent). It is not a mechanism in which the user designates programs to be kept resident, so this is wrong.
ここがポイント
- Cache memory is a high-speed, small-capacity memory that bridges the speed gap between the CPU and the main memory, and its purpose is to shorten the effective (average) access time.
- The effectiveness of the cache is determined by locality of reference and the hit ratio, and storing is controlled automatically by the hardware (not designated by the user).
用語