問70
頻出度★★☆
次の記憶装置のうち, アクセス時間が最も短いものはどれか。
平成31年度 春期 ITパスポート試験 問70
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 70
Incorrectア
An HDD reads and writes by spinning magnetic disks and mechanically moving the magnetic head to the target position. Because it involves mechanical motion, it has the longest access time of the four — the exact opposite of the fastest.
Incorrectイ
An SSD uses flash memory and, having no mechanical motion, is faster than an HDD; but its access time is longer than that of semiconductor memories such as the cache memory right next to the CPU and the main memory, so it is not the fastest.
- ウ
正解 Storage devices form a “memory hierarchy” in which the closer a device is to the CPU, the faster it can be accessed. Ordered from fastest to slowest: the registers inside the CPU → cache memory → main memory → SSD → HDD. Cache memory sits between the CPU and main memory and uses fast semiconductor memory (SRAM), so among the four choices it has the shortest access time. Therefore the correct answer is “ウ”.
Incorrectエ
Main memory (DRAM) is faster than an SSD or HDD, but its access time is longer than the cache memory, which is closer to the CPU and uses SRAM. The cache is a memory faster than main memory, placed to speed up access to main memory.
ここがポイント
- The memory hierarchy, from shortest to longest access time: registers → cache memory → main memory → SSD → HDD. The closer a semiconductor memory is to the CPU, the faster it is.
- Cache memory is fast SRAM placed between the CPU and main memory; it supplements access to main memory and has the shortest access time among the four choices in this question.
用語