The processor: what GHz and cores really mean
Read a computer’s specification and know exactly what the numbers are promising you.
The processor — the CPU — does the thinking. What “thinking” means here is far narrower than it sounds. It picks up an instruction, works out what the instruction means, does it, and writes the answer down. Then it does the next one.
Each instruction is tiny: add two numbers, compare two numbers, move something from here to there. Everything else — a photograph appearing, a video playing, this sentence arriving on your screen — is built out of billions of those.
Key points
- A processor fetches, decodes, executes and stores — billions of times a second
- Gigahertz is how many times a second; cores is how many workers
- Gigahertz cannot be compared across generations, so treat the number with caution
- Cores help work that divides; they do nothing for work that must happen in order
What to remember
- Four steps, in a fixed order, repeated for ever. That is genuinely the whole job.
- Notice that a second core did not halve the time for everything. Some work has to happen in order, and no number of workers can change that.
- Cores are width. Gigahertz is speed. Choose width when you do many things at once, and speed when you do one thing at a time.
- If you cannot describe the job as several things happening at the same moment, extra cores will not shorten it.
Try this
Look up the processor in your own machine — About your PC on Windows, About This Mac on a Mac — and search the internet for its name followed by the word benchmark. You will find a score you can compare directly with any other machine, and it is a far better guide than gigahertz.
Practice: The processor: what GHz and cores really mean. Your first lesson is free, with no account or card; the rest are part of a Lantern plan. Interactive lessons require JavaScript.