Cores

A core is one of the processing units built into a CPU chip. Each core can carry out the fetch–decode–execute cycle on its own, so a single core works much like a small, complete CPU, and a multi-core processor simply has several of these units on one chip.

Naming CPUs by their cores

The number of cores is part of how a CPU is described, and the common names simply count them:

So an octa-core CPU contains eight processing units that can each work independently.

Why more cores help

More cores allow more instructions to be processed at the same time, which is called processing in parallel. With one core, instructions have to wait their turn and are dealt with one after another. With several cores, work can be shared out, so fewer instructions are left waiting.

This pays off when several programs are open at once. Imagine a tablet with a quad-core CPU running a video call, a note-taking app and a music player. The operating system can share these three programs across the four cores, so the video call keeps a steady picture while your typing still appears instantly. On a single-core CPU the same jobs would have to take turns, and the typing would feel sluggish.

It also helps with one large job, as long as that job can be split into parts that do not depend on each other. A quad-core CPU could work on four sections of a task at the same time rather than tackling them one by one.