CPU

The CPU is the main processor of a computer. It sits as a small chip on the motherboard and executes what a program instructs it to do. Its work consists of very simple steps: adding numbers, comparing values, fetching data from memory. Because it does this billions of times per second, everything from word processors to video games emerges from it. The abbreviation stands for “Central Processing Unit,” i.e., central computing unit. You can think of it as the workstation where all of a device’s tasks come together.

The all-rounder in every device

No computer runs without a CPU. It starts the operating system, manages memory, and passes tasks on to other components. Your phone, your router, and even the washing machine have one too, just smaller and more power-efficient. The CPU is the generalist among chips: it can run any kind of program, rather than just one type of calculation.

This very versatility is both its strength and its limitation. Other chips are specialized for a single task and are much faster at it. The best-known example is the graphics card, or GPU for short. It can handle thousands of similar calculations at the same time, while a CPU only processes a few tasks in parallel.

For artificial intelligence, this difference is crucial. Training large AI models consists of vast numbers of very similar multiplications. On CPUs, this would take years; on GPUs, it takes weeks. That’s why for years now it has mainly been the stock price of graphics chip manufacturers that has been rising, not that of traditional CPU companies. Still, a common misconception is that the CPU has become obsolete. It continues to control the overall process and supplies the specialized chips with data.

Clock speed, cores, and the path of an instruction

A CPU works in a fixed rhythm, the clock. At 3 gigahertz, this rhythm beats three billion times per second. In each step, the processor fetches an instruction, decodes it, and executes it. An instruction is tiny, something like: add these two numbers. Only the interplay of billions of such steps produces a visible result on the screen.

Modern CPUs consist of multiple cores. Each core is essentially its own processor on the same chip. An eight-core chip can therefore genuinely handle eight tasks at the same time. So that the cores don’t have to wait for data, a very fast intermediate memory, the cache, sits right next to them. It keeps the numbers ready that are needed frequently at the moment.

Higher clock speeds mean more heat and more power consumption. That’s why clock frequencies have barely increased since around 2005. Instead, manufacturers add more cores and make the components ever smaller. Current chips work with structures just a few nanometers in size, that’s a millionth of a millimeter.

From Intel and AMD to the Apple chip

In laptop product descriptions, the CPU is usually listed right at the top. Names like Intel Core, AMD Ryzen, or Apple M4 denote processor families. The numbers that follow roughly indicate the performance class. For everyday use, what matters most is how many cores the chip has and how power-efficient it is.

The CPU regularly appears in business news. One topic is the shift by many manufacturers to chips with ARM architecture, which require less power. Apple has made this move in its Macs, and others are following suit for servers. A second topic is the dependence on just a few factories, especially in Taiwan. Who produces there and who doesn’t has since taken on political significance.

The CPU also remains present in AI data centers. It prepares data, distributes tasks, and keeps the graphics chips busy. When you ask a chatbot a question, a CPU is involved in routing it. The actual computational work of the model, however, is then handled by the specialized chips alongside it.