ITPEC IP October 2020 Question 12

The number of cores is the number of processing units built into the CPU, as in dual-core and quad-core CPUs — each core executes instructions on its own.

The items in the table:

• •Operating frequency (clock frequency): the number of clock signals per second, in GHz, that time the CPU's operations; for the same design, a higher frequency means faster processing
• •Number of cores: the processing units in one CPU; a dual-core CPU has two, a quad-core four, and each can run different processing at the same time
• •Number of threads: the instruction streams the CPU can execute at once; with multithreading one core runs two, so a 4-core CPU may show 4/8
• •Cache memory: fast memory inside the CPU; the primary (L1) cache sits next to each core, the secondary (L2) behind it

Answer (b)

Why not others:

• •(a) — the definition of operating frequency is right, but speed rises with frequency: it is proportional, not inversely proportional, since more clock cycles per second execute more instructions
• •(c) — more threads let more processing run in parallel, so a smaller number does not mean faster processing
• •(d) — the order is reversed: the primary cache is closest to the core and is checked first; the secondary cache is larger, slower and further away

Key rule: Cache levels are numbered outward from the core: L1 is the smallest and fastest, L2 and L3 are larger and slower, and main memory comes after them.

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