A generic model, such as the five-register cycle you traced, teaches ideas. A real product has its own design, so your answer should use the model for ideas and use only the figures the question gives for the device.
This lesson completes hardware and processing. It follows justifying an input-output choice and applies the same rule: stay with the situation in the question.
What can I claim, and what can I not?
| Safe to say | Unsafe to say |
|---|---|
| “In the simplified model, the PC holds the address of the next instruction.” | “This laptop’s processor has a register called MAR in exactly this way.” |
| “The question gives 3.2 GHz, so it completes 3.2 billion cycles per second.” | “Brand X laptops always have 16 GB of RAM.” |
| “More cores can allow more instructions to be worked on at once, if the software can use them.” | “A 4 core processor is four times faster.” |
| “A larger cache can reduce waits for data from slower memory.” | “This product has the largest cache, so it is the fastest.” |
Three ideas often appear in comparison questions.
Clock speed is the number of cycles per second. Cores are separate processing units, each able to run its own instructions. Cache is small, very fast memory close to the processor that holds data and instructions used often.
Worked example
A question describes two laptops.
Laptop A: 2.0 GHz, 2 cores. Laptop B: 3.2 GHz, 4 cores, a larger cache. A student writes that B is “12.8 GHz” and is certainly faster. Correct the answer.
Step 1, clock speeds. A is 2.0 GHz = 2 000 000 000 cycles per second. B is 3.2 GHz = 3 200 000 000 cycles per second. The ratio is 3.2 ÷ 2.0 = 1.6.
Step 2, the cores claim. The student multiplied 3.2 × 4 = 12.8. This is not valid: cores do not add their clock speeds together. Each core runs at about 3.2 GHz, and having four cores lets more instructions be worked on at once, only when the program can use them.
Step 3, a safe comparison. “Laptop B has a higher clock speed (3.2 GHz against 2.0 GHz), more cores and a larger cache, so it is likely to process instructions more quickly for suitable tasks. The actual speed also depends on the software.”
Notice the careful words “likely” and “for suitable tasks”. They are not weak hedging; they match what the data can support.
The mistake to watch for
Students bring in a remembered fact from advertising and write it as if it were part of the question.
Mistaken answer: “Laptop B is made by a famous brand, so its processor is reliable and has hyper-threading.”
The question never says this. A claim about a brand’s design cannot be proved from a generic model or from the data given.
Correct it by deleting anything the question or the model does not give you, and rewrite using the figures supplied: clock speed, cores, cache, RAM size, storage type.
Check yourself
1. A processor runs at 2.5 GHz. How many clock cycles is that per second?
Show answer
2.5 × 1 000 000 000 = 2 500 000 000 cycles per second (2.5 billion).
2. A student says: “A 4 core processor at 2 GHz is the same as an 8 GHz processor.” Give one sentence correcting this.
Show answer
Cores do not combine their clock speeds: each core still runs at 2 GHz, and four cores help only when the program can use them at once.
3. Which of these needs the question to supply it before you can state it: (a) the PC holds the next address, (b) Phone Z has 6 GB of RAM, (c) RAM is volatile?
Show answer
(b). (a) and (c) are general ideas from the model. A figure for a specific phone must be given in the question.
Where this leads next
You have now covered the whole module. Test it with the hardware and processing practice set, then continue to software and systems. The mistake log and retest queue is useful for noting every claim you had to delete.
Using exactly the information the question gives sounds simple but takes practice. Our teachers in online one-to-one Computer Science tuition can review your written answers with you line by line.