How Computers Think: Inside the CPU

🔥 Why CPUs Get Hot

Inside a CPU are billions of tiny switches. These switches flip between off (0) and on (1). Every time a switch flips, it uses a little bit of energy ⚡. When billions of them flip billions of times each second, all that energy adds up.

And energy doesn’t just vanish—it turns into heat 🔥.

That’s why a CPU gets hot. It’s not “angry,” it’s just working really hard. If the heat gets too high, the CPU will slow down to protect itself. This is called throttling. If it gets even worse, the CPU may shut off completely to stay safe.

To stop overheating, computers use cooling systems:

A heatsink 🧊: a block of metal that spreads the heat out.
A fan 🌬️: blows the hot air away.
Water cooling 💧: tubes carry heat away, just like pipes in your house carry water.

💬 How CPUs Speak Different “Languages”

Every CPU needs a language to understand what programs want. This language is made of instructions, like:

“Add these numbers”
“Store this value”
“Jump to another step”

The set of instructions a CPU understands is called its instruction set. It’s like the rules of a board game 🎲. Once you know the rules, you can play.

Different CPUs may have slightly different rules, but they’re all playing the same kind of game: taking instructions and carrying them out.

Two Styles: RISC and CISC

Over time, engineers designed CPUs in two main styles.

RISC (Reduced Instruction Set Computer)

RISC chips keep things short and simple. Each instruction is small and clear. To do something big, a RISC CPU may take several small steps, but each step is fast and predictable.

CISC (Complex Instruction Set Computer)

CISC chips have many instructions, and some can be very complicated. For example, one instruction might say:
“Take this number, multiply it by that number, and store the result.”

That sounds powerful. But inside, the CPU usually has to break it into smaller steps anyway.

Think of it this way:

RISC = small bites of food 🍽️.
CISC = trying to eat the whole sandwich in one bite 🥪, but still chewing it little by little.

📱 ARM: The RISC in Your Pocket

One of the most famous RISC families is called ARM. ARM chips are in almost every phone, many tablets, and even laptops like Apple’s M1 and M2 Macs.

ARM chips are excellent at saving energy, which is why your phone lasts all day without a giant fan.

How ARM does it:

Uses simple instructions → easy to handle.
Has big.LITTLE cores:
- Big cores = powerful, but use more energy.
- Little cores = slower, but save energy.
Packs everything—CPU, graphics, memory controller—onto one chip (called a System on a Chip, or SoC). Since parts are close together, signals travel shorter distances, saving power and reducing heat.

💻 x86: The Powerhouse in Your PC

Most desktops and laptops use x86 CPUs, which belong to the CISC family (made by Intel and AMD).

These CPUs are very powerful and can run complex programs, including older ones. They are great for:

Gaming 🎮
Video editing 🎬
Scientific work 🔬

But they also use more power and make more heat. That’s why gaming computers often have several fans, large heatsinks, or even water cooling.

🌟 RISC-V: A New Player

A newer style is RISC-V. Like ARM, it’s simple and efficient. But here’s the special part: it’s open. Anyone can design a CPU with it without paying for a license.

That’s why universities, hobbyists, and startups are excited about it—you’ll probably hear more about RISC-V in the future.

🧩 Why These Designs Matter

ARM → best for phones and tablets because it saves energy and stays cool.
x86 → best for desktops and servers because it delivers raw power, even if it gets hot.
RISC-V → may spread into gadgets, smart devices, and even bigger computers later.

In the end, all CPUs do the same work: flipping switches between 0 and 1. But the style of how they follow instructions changes how much energy they use, how much heat they make, and what devices they’re best for.