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Your computer uses a microprocessor to do its work. Smaller and thinner than a dime, this tiny silicon chip contains millions of transistors that work together to help you do everything from write a school report to search the Web for the current population of the Svalbard Islands.

But what really is a microprocessor? How are they made? And how do they do all the things they do?

Lesson 1: The Robotic Arm

For you, reaching out and picking up an object requires little thought. But for a microprocessor, such actions require lots of precise instructions. Programming a robotic arm to make something like a peanut butter-and-jelly sandwich could take hundreds of instructions. That is why in factories using robotic devices, each device is usually designed and programmed to do just several steps of the manufacturing process over and over again. The item being manufactured goes from one robotic station to the next until it is completed.

Try Activity 1: The Robotic Arm >

Lesson 2: Fetch, Decode, and Execute

Whether you're playing a game, writing a report, or surfing the Web, the microprocessor in a computer processes your data using the same three steps over and over again. It does these three steps at incredible speed—millions of times a second. Here are the three steps and a short explanation of each:

  1. Fetch—Microprocessor gets a software instruction from memory telling it what to do with the data.
  2. Decode—Microprocessor determines what the instruction means.
  3. Execute—Microprocessor performs the instruction.

Try Activity 1: Fetch, Decode, and Execute >

Try Activity 2: Fetch, Decode, and Execute in a Chip >

Try Activity 3: Make River Fetch >

Lesson 3: The Best Things Come in Small Packages

Pluck a hair from your head. (Really.) Now look at it. It isn't very thick, is it? Well, to a microprocessor manufacturer, that hair looks like a telephone pole. That's because a hair is more than 2000 times wider than a transistor on a microprocessor. Wires between transistors are even thinner. They're more than 4000 times thinner than a hair.

See a human hair up close >

How big is a human hair? About 100 microns in diameter. That means a transistor is just 0.045 microns wide.

What's a micron? It's a very small metric measurement. You're probably familiar with centimeter marks on a ruler. (If not, go look at one.) A micron is .0001 of a centimeter.

A microprocessor transistor then is 0.0000045 centimeters wide. (Want that in inches? It's 0.00000177 of an inch.)

Try Activity 1: How Many Transistors on the Head of a Pin? >


Journey to the Center of a Microprocessor

It is impossible to see the incredibly small transistors and circuits in a microprocessor with your eyes, but with a microscope you can.

Use the different magnification powers of this virtual microscope to see the inner workings of a microprocessor. At the highest magnifications, you see actual circuit paths.

Try Activity 2: Journey to the Center of a Microprocessor >

*Note this animation only works in Mozilla Firefox* and Microsoft Internet Explorer*

Microscopic Dust

A lot of dust is so small we cannot even see it. But with a microscope, you can. Use the different magnification powers of this virtual microscope to see how big a microscopic speck of dust can be compared to circuits in a microprocessor. Since a single speck of dust can ruin a microprocessor, you can see how important it is to manufacture microprocessors in virtually dust-free facilities.

To protect chips from dust during the manufacturing process, they are made in clean rooms. Clean rooms are 10,000 times cleaner than a hospital operating room.

Try Activity 3: Microscopic Dust >

*Note this animation only works in Mozilla Firefox* and Microsoft Internet Explorer*

Lesson 4: How Do They Make Chips so Small?

Before a microprocessor can be manufactured, it has to be designed. This is no easy task. It takes a team of up to 600 engineers. The engineers face a task equivalent to trying to design a small city from the ground up. How much area of the chip should be set aside for temporarily storing information? How much area should be set aside for maintaining instructions currently being used? How much area should be dedicated to accepting information?

Once the areas of the chip have been mapped out by purpose, the circuitry has to be designed down to the individual transistor. With over 500 million of them in modern microprocessors, that's a lot to keep track of. It's like building a city by designing every room in every home and building before you even pick up a brick.

Lesson 5: Recipe for a Microprocessor

While the process of designing and manufacturing a microprocessor is extremely complex, the ingredients are rather simple. In the most elemental terms, microprocessors are compised of quartz, metals, chemicals and water. Think about that the next time your computer is spell checking your 12-page report on Patagonia cavies and other South American quadrupeds.

Try Activity 1: Microscopic Ingredients >

Lesson 6: Building Skyscrapers on a Wafer

Ever hold a 20-story building in the palm of your hand? That's what it's like holding a dime-sized microprocessor with millions of transistors.

A single microprocessor is like a miniature skyscraper with stairway-like circuits between each floor. Hundreds of these "skyscrapers" can be produced on a silicon wafer at a time.

See a wafer up close >

From start to finish, a microprocessor takes about 2 months to produce. Fabrication begins with a very thin slice of silicon. Over 300 manufacturing steps later, this silicon wafer holds hundreds of microprocessors. If you could enlarge the wafer to the size of a swimming pool, the surface would look like a miniature city.

Now think small and ask yourself this: How are such tiny circuits put in such a small chip? Good question. No mechanical object or pen could lay down such incredibly microscopic wires. Instead, the pathways for the current are created by using solvents to remove channels of material. These microscopic channels are then etched with chemicals and implanted with electrons to make them conduct electricity.

Try Activity 1: Make a Circuit on a Wafer >


Explore a Microprocessor

This activity lets you select and view sections of a chip at a fixed magnification. Imagine you are putting a microprocessor on a microscope slide and moving it around under the lens.

Start with Select. Use your pointer to grab and drag the white circle to the part of the chip you want to view. Use the Focus, Intensity, and Zoom controls to perfect your image.

As you examine the microprocessor, think how different areas of the chip handle various tasks. Can you tell what this particular area of the chip does—fetch, decode, or execute?

Unless you are a chip designer, it would be hard to guess. Today's advanced microprocessors with their multiple layers and millions of transistors are too complex. What conclusion can you make? There is incredible processing power for all three tasks in something smaller than your fingernail.

Try Activity 2: Exploring a Microprocessor >

*Note this animation only works in Mozilla Firefox* and Microsoft Internet Explorer*

Exploring Chip Layers

Chips may look flat, but they can have as many as 20 layers. Each layer is full of tiny pathways that make up the circuits and transistors of the chip. There are also microscopic connections running between one layer and another.

This activity lets you move between the several layers of a chip by focusing on various depths. Use the Focus Depth control to change the layer visible through the microscope.

Try Activity 3: Exploring Chip Layers >

*Note this animation only works in Mozilla Firefox* and Microsoft Internet Explorer*

Want To Learn More?

Explore these links to learn more about microprocessors.

From Sand to Silicon: The Making of a Chip >

Microprocessor Manufacturing Photos >

Microprocessor Quick Reference Guide >

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