#21 Jun 2024 Q6(c) 3 marks 1.1.2 — CPU performance characteristics

Question

Q6 stem: A computer has a Central Processing Unit (CPU).

6(c) Give three characteristics of a CPU that can affect its performance.

  1. ....................................................................................................
  2. ....................................................................................................
  3. ....................................................................................................

[3]

Why this question is tricky

Candidates were often able to identify at least one characteristic of a CPU, most commonly the clock speed and number of cores. Some responses were not precise enough as to the characteristics, for example stating ‘clock’ or ‘core’ without reference to the speed of the clock, or the number of cores, which were too ambiguous.— J277_01_ER_Jun2024.txt lines 337–341

MS complexity 4/10: 1 mark each to max 3, but the MS explicitly lists 'clock', 'cache', 'speed', 'cores' as NE (not enough) — bare nouns score zero. Each characteristic must be a measurable quantity.
Specific traps:
  • Bare-word answers rejected: single nouns (‘clock’, ‘cache’, ‘cores’) score 0.
  • “Clock speed on its own is NE” in some contexts — phrase it as a measurable property the CPU has.
  • “Speed” alone is too ambiguous (could mean clock, bus or RAM).
  • Listing three CPU components (ALU, CU, registers) instead of three performance characteristics scores 0.
  • Repeating the same characteristic with different wording (e.g. “fast clock” + “high clock rate”) scores once.

Full-marks model answer

  1. Clock speed — the frequency at which the CPU executes the fetch–execute cycle (measured in GHz); a higher clock speed means more instructions can be processed per second.
  2. Cache size — the amount of fast memory built into the CPU; a larger cache stores more frequently used instructions and data so the CPU spends less time waiting for main memory.
  3. Number of cores — each core can execute its own fetch–execute cycle simultaneously, so more cores allow more instructions to be processed in parallel.
Mark allocation (3 marks — 1 mark each to max 3)
  • Clock speed (qualified) → MS bullet “Clock speed on its own is NE” (phrased as clock speed with reference to frequency, not bare “clock” or bare “speed”) — J277_01_MS_Jun2024.txt:611–612.
  • Cache size → MS bullet “Cache size” (not bare “cache”) — J277_01_MS_Jun2024.txt:613.
  • Number of cores → MS bullet “Number of cores” (not bare “cores” or “core”) — J277_01_MS_Jun2024.txt:614.

Watch out for...

The Examiner Report flags that many candidates wrote bare nouns like “clock” or “core” and lost marks for being too ambiguous. Every characteristic must be expressed as a measurable quantity — “speed of the clock”, “size of the cache”, “number of cores”, not just the noun. Three precise phrases score 3; three bare nouns score 0. Also avoid listing CPU parts (ALU/CU/registers) — those are components, not performance characteristics.