← ACARA Digital Technologies Years 7–8

Clock speed or more cores: which helps which task

Higher clock speed (GHz) speeds up one task at a time; more cores help when many tasks, or a task split into parts, run together. Quad-core is not always 4x faster.

Part of: ACARA Digital Technologies Years 7–8 — Hardware and Performance — Module 13

Understanding Clock speed or more cores: which helps which task in ACARA Digital Technologies Years 7–8

What it does: Video export splits into parts that run in parallel, so more cores finish the job sooner. Some steps must run one after another, so four cores give less than four times the speed. A task that uses one core at a time finishes faster when that core runs faster. Extra cores would sit idle. Clock speed is how fast a core works. The number of cores is a separate spec. Each core can work on a different task or a different piece of the same task together.

Common mistakes: One job means a single task running at a time, so the test should be jobs == 1. Higher clock speed speeds up one task. jobs > 1 would describe many tasks. With many tasks running together, extra cores let them run side by side. The message should say more cores help, not fewer.

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Learning
Duo
Your old single-task game runs on only one core and feels slow. Which upgrade helps most?
A CPU with a higher clock speed (GHz)A CPU with more cores
Matches
Many programs open at once is slow, so buy a higher GHz single core only
↓
Many programs open together is a many-tasks job, so more cores would help more than clock speed alone
Applying
Meanings
Term
clock speed vs cores
Meaning
Higher clock speed (GHz) speeds up one task at a time; more cores help when many tasks, or a task split into parts, run together. Quad-core is not always 4x faster.
Practice
IF task is one single demanding job THEN
Testing
Gaps
IF oneTask THEN raise speed
Check Answer
Spots
1jobs = 1
2if jobs > 1:

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Quick Questions

1. Your old single-task game runs on only one core and feels slow. Which upgrade helps most?
A. A CPU with a higher clock speed (GHz) ✓
B. A CPU with more cores
A task that uses one core at a time finishes faster when that core runs faster. Extra cores would sit idle.
2. You have a browser, music, a chat app and a document all open at once. What helps most?
A. More cores, so programs can run side by side ✓
B. Only a higher clock speed
Many open programs can each use a different core at the same time. That is why more cores help with multitasking.
3. Which statement is true about clock speed?
A. A higher GHz adds extra cores to the CPU
B. A higher GHz makes a core finish its steps faster ✓
Clock speed is how fast a core works. The number of cores is a separate spec.
4. A video editor exports a video. The software splits the work into parts. Which CPU suits it better?
A. 2 cores, because video export only uses one core
B. 8 cores, because the parts can run at the same time ✓
Video export is often split into chunks, such as groups of frames. Each core can work on a chunk together.
5. A quad-core CPU is always exactly four times faster than a single-core CPU. True or false?
A. False ✓
B. True
Not every task can be split into four equal parts. Some steps must wait for others, so the speed-up is usually less than 4x.

Match the Pairs

cpu.clock = 4.5 GHz → A higher clock speed makes a single task run faster, because each core finishes its steps more quickly
cpu.cores = 8 → More cores let many programs, or one job split into parts, run at the same time
Exporting a video can be split into parts, so extra cores can each work on a chunk at the same time → export_video(cores = 8)
A quad-core CPU is not always 4x faster, because some of the task cannot be split across cores → speedup < 4 * single_core
Many programs open at once is slow, so buy a higher GHz single core only → Many programs open together is a many-tasks job, so more cores would help more than clock speed alone
quad_core_time = single_core_time / 4 → This assumes a perfect 4x speed-up, but parts of a task cannot be split, so the real gain is smaller

Key Term

clock speed vs cores
Higher clock speed (GHz) speeds up one task at a time; more cores help when many tasks, or a task split into parts, run together. Quad-core is not always 4x faster.

Fill in the Blanks

1. oneTask = TRUE IF oneTask THEN raise clock speed ENDIF
Hint: Type the CPU feature, measured in GHz, that you raise to speed up a single demanding task.
2. openApps = 8 IF openApps > 4 THEN add cores ENDIF
Hint: Type the CPU part that lets many programs run at the same time.
3. exportParts = 4 IF exportParts > 1 THEN PRINT "use many cores"
Hint: Type the comparison operator that checks whether the video export is split into more than one part.
4. speedup = 3.2 IF speedup < 4 THEN PRINT "not 4x faster"
Hint: Type the comparison operator showing that a quad-core is often less than four times faster.
5. speed = 3.6 GHz IF speed > 3 THEN PRINT "fast one task"
Hint: Type the unit used to measure CPU clock speed.

Spot the Error

Question 1
A jobs = 1
B if jobs > 1:
C print("Higher GHz helps")
Line B — One job means a single task running at a time, so the test should be jobs == 1. Higher clock speed speeds up one task. jobs > 1 would describe many tasks.
Question 2
A jobs = 6
B if jobs > 1:
C print("Fewer cores help")
Line C — With many tasks running together, extra cores let them run side by side. The message should say more cores help, not fewer.
Question 3
A cores = 4
B parts = 8
C t1 = 40 # mins on 1 core
D ideal = t1 * cores
Line D — An ideal video export split across 4 cores takes the one-core time divided by the number of cores. Multiplying would make the export take longer, which is wrong.
Question 4
A unit = "GB"
B speed = 3.6
C print(speed, unit)
Line A — CPU clock speed is measured in gigahertz (GHz). GB means gigabytes, which measures storage or memory size.
Question 5
A cores = 4
B real_speedup = 2.8
C print(real_speedup == cores)
Line C — A quad-core is not always 4x faster, because some work cannot be split up. The real speedup is usually less than the number of cores, so it should use <.

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