問51
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互換CPUに関する記述のうち, 最も適切なものはどれか。
平成27年度 春期 ITパスポート試験 問51
テクノロジ系コンピュータ構成要素 › プロセッサ
This question's explanation and your answers so far.
解説
問 51
- ア
正解 The correct answer is ア. A compatible CPU (compatible processor) is a CPU made by a different manufacturer that is designed to have the same instruction set architecture as some manufacturer's CPU. As long as the types and formats of machine-language instructions that the CPU can understand (the instruction set) are the same, an OS or application software written as such an instruction sequence can run as-is, without rewriting or recompiling the program. In other words, the very purpose of a compatible CPU is “to let software assets built for the original CPU run without modification”, and the description in ア states this correctly.
Incorrectイ
Incorrect. What a patent protects is the specific internal implementation technology (circuit design or method of realization), not the instruction set itself, which is a “specification / interface”. Makers of compatible CPUs realize the same instruction set with their own circuit designs that do not infringe the patents, or they conclude cross-licensing agreements, and in this way they legally develop and manufacture their products even while the patents on the original CPU are still in effect. In fact, x86-compatible CPUs have competed in the market alongside the original products in the same era.
Incorrectウ
Incorrect. Whether a CPU is single-core or multi-core is merely a difference in implementation-level configuration — how many processing cores are placed inside the CPU — and is a separate matter from instruction set compatibility. There is therefore nothing preventing the creation of multi-core compatible CPUs, and in fact multi-core compatible CPUs widely exist as products.
Incorrectエ
Incorrect. Compatible CPUs are not only for extending the life of or boosting the performance of old PCs (as replacement parts). As equal products that compete with the original CPU on price, performance, power consumption and so on, they are also adopted as the standard CPU in newly designed and newly sold PCs. The assertion that it “is never adopted in new PC products” is contrary to fact.
ここがポイント
- Compatible CPU = a CPU from another manufacturer that has the same instruction set architecture as the original CPU. Because the instruction set is the same, the same OS and application software can be run as-is (the aim is to secure compatibility of software assets).
- Compatibility of the instruction set (the specification) is a different dimension from the internal implementation (circuits and manufacturing technology, which is what patents cover) and from the number of cores (single-core / multi-core). Being compatible does not mean the internals are identical either, and compatible CPUs are competing products that are adopted in new products as well.
用語