Processor Fundamentals and Assembly Language: Question 1
Syllabus 4.1
A student lists several features of a computer system and wants to identify which one is a genuine factor affecting the performance of the CPU itself, rather than a feature of a different component.
Which of these is a factor that directly affects the performance of a CPU?
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Worked solution
Why cache memory affects CPU performance
Cache memory is small, very fast memory built into (or very close to) the processor. It stores copies of instructions and data that the CPU has used recently or is likely to need again soon. Because reading from cache is much faster than reading from main memory, a larger cache means the CPU is more likely to find what it needs already close by, so it spends less time waiting for slower main memory. This directly increases the number of instructions the CPU can complete in a given time, it directly affects performance.
Other genuine factors affecting CPU performance include clock speed (how many fetch-execute cycles can occur per second), the number of cores (how many instructions can potentially be processed in parallel) and the width of the buses (how much data or how many addresses can be handled at once).
Why the other options are wrong
- B (monitor resolution): affects the quality/detail of the image displayed, which is a property of the monitor and graphics output, not of the processor’s own instruction-processing performance.
- C (hard disk storage capacity): affects how much data and how many files can be stored long-term; it does not make the CPU itself fetch, decode or execute instructions any faster.
- D (keyboard layout): affects how a user physically types, and has no effect on the internal operation of the processor.
Final answer
A. The size of the cache memory is a genuine factor affecting CPU performance, because it changes how often the processor can access data it needs quickly rather than waiting on slower main memory.