Inside the CPU: Fetch, Decode, Execute · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Fetch it, read it, run it

Computing · Computer Systems · ages 15-16
Name ______________________   Date ____________
  1. Where does fetch grab the next instruction from?

    • Memory
    • The screen
    • The keyboard
  2. What is the correct order of the cycle?

    • Decode, fetch, execute
    • Fetch, decode, execute
    • Execute, fetch, decode
  3. Which part does the maths once decode has spoken?

    • The cache
    • The clock
    • The ALU
  4. Two chips share a clock, but one has double the cores. What best follows?

    • It always runs exactly twice as fast
    • It can chew more tasks side by side
    • It needs no memory at all
  5. A 3 GHz processor runs about how many billion cycles per second?

    Answer: ______________

  6. Why does a bigger cache make a machine feel faster?

    • Recent bits wait nearby, so fetches hurry
    • It raises the clock speed
    • It adds more cores
  7. Why must data sit in memory next to instructions during a run?

    • Data looks nice beside code
    • Memory deletes data otherwise
    • Execute reads and stores its working values there
  8. Two cores are always exactly twice as fast as one.

    Circle one:   True   False

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Fetch it, read it, run it W1-mt_YT-FSWnUKR-s1

  1. Memory · Every next instruction waits in memory for its fetch.
  2. Fetch, decode, execute · Each round fetches first, works out the meaning, then acts.
  3. The ALU · The ALU crunches numbers and comparisons at execute time.
  4. It can chew more tasks side by side · Each core runs its own cycle, so tasks advance in parallel.
  5. 3 · 3 GHz means about 3 billion rounds each second.
  6. Recent bits wait nearby, so fetches hurry · Nearby copies spare the trek to main memory.
  7. Execute reads and stores its working values there · Each step works on values waiting in memory, not only in storage.
  8. False · Cores split parallel work, but some jobs refuse to split.
Worksheet · LightMySky