CPU: Here's what to know about the heart and mind of computer-based devices

Many call it the brains of a computer, but the CPU is more than that.
Stephen Vicinanza
Technician holding a CPU
Technician holding a CPU.

Jae Young Ju/iStock 

  • The Central Processing Unit is made up of cores layered on top of each other.
  • CPU's come in many sizes and speeds.
  • Modern CPUs can make billions of calculations per second.

The CPU is the Central Processing Unit of a computer-based device. It is at the heart of all computers and does much of the calculating and processing of data.

Many people believe it is the "brains" of a computer. CPU is all of that and more. It is also a storage location for instructions and can serve as a link to artificial intelligence, which infers new instructions for the computer's routines. It also drives graphics and games, which are becoming smaller, faster, and more "intelligent" every day.

The CPU regulates information flow within computer systems, much like the heart that beats in human bodies. The computer, phone, tablet, or other gadget depends on that flow for its operation.

Let's dive into the computer's heart: the CPU.

What is a CPU?

CPU: Here's what to know about the heart and mind of computer-based devices
Clean room technician with wafer

The Central Processing Unit is the principal part of any digital computer system. There are three main parts to a CPU; there is the main memory, or register, the control unit, and the arithmetic unit. These component parts are made up of processing units called cores, and when taken together, these cores form an Integrated Circuit Chip called the Microprocessor.

When being manufactured, the cores are made of silicon, plastic, and copper and are referred to as wafers. This happens in the sterile environment known as a "clean" room at the facilities where they are made. Workers must don specialized clothing that covers their entire body and resembles space suits or hazmat suits.

In its most basic form, those cores are a series of tiny simple switches that are either on or off. This is designated as 1 = on and 0 = off. They are arranged in a series of 8 switches per byte, and each switch is considered a bit.

For example, the sequence 01000001 represents the letter A, and so on. This is commonly referred to as Machine Language, because that is the only way a computer can make computations, through electro-mechanical 1 and 0's.

The CPU uses a particular type of memory, called cache (pronounced cash). This is an extra bit of memory that can be retrieved at high speed, for performing tasks such as graphic transfer and data that needs to be accessed for specific purposes such as processor routines not otherwise used by the computer. This can include high-level mathematics and calculations. The cache is usually very small, generally between 64k and 256k.

There are also bus connections, such as a wire or optical fiber, etc., used to connect different computer components and transfer data between them. In the CPU, the bus is usually located on the motherboard (the board all the internal components are placed) and holds the pins on the bottom of the CPU to the motherboard, connecting the CPU to the rest of the computer components.

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There is also the speed at which operations occur within the CPU, called the Clock Cycle, or just the clock. This is the time between pulse synchronization of an oscillator. In simple terms, how fast the processor calculates is measured today in gigahertz, or billionths of a second.

There are two clocks in a desktop computer, or computer-driven device, the hardware or physical clock, which is usually called a real-time clock, and the software clock, which is the one usually referred to as the System Clock, where the speed designations are usually gleaned from.

Most of us know that computer memory and sizes of distribution are measured as Kilobyte, Megabyte, Gigabyte, Terrabyte, etc. Most early computers ran in 256 bytes and 512 bytes of data processing. It could take an hour to download a file from the internet that was relatively small in size, through an old-style dial-up modem. Today's computers are much larger and much faster.

What does a CPU do?

CPU: Here's what to know about the heart and mind of computer-based devices
The flow of data in computers

The CPU performs many operations, including regulating and integrating operations of the computer. This is performed by the control unit (core). The CPU selects and retrieves instructions from the main memory (core) in proper order and interprets those instructions in order to activate the other functional elements of the system. This data is then directed to the arithmetic unit (core) for processing and distribution throughout the system.

The arithmetic-logic unit (ALU) performs arithmetic and logical operations (which can be thought of as decisions), it is where calculations are done and it also acts as a gateway between primary memory and secondary storage. Data transferred between them passes through the ALU.

The basic flow of data is from control (which is analogous to the left ventricle in the heart) to memory, (where the oxygen is stored) to the arithmetic unit (like the right ventricle out into the arteries and vessels).

It is a cycle that happens millions of times a second, much faster than a heart beats.

What does a CPU do in a computer?

The CPU runs the apps on a computer, makes calculations, and produces results for the programs it is running. Essentially, it crunches the data that is placed in it from external sources. This can include datasets, raw data, software apps, and graphics. It can perform many types of tasks, as well as evaluate those tasks for optimal efficiency.

The common tasks a computer CPU might handle are complex mathematical calculations, long lists of data collection, running a web browser, calling a phone number, and keeping lists of contacts and information in databases.

The faster the speed at which a CPU runs, the more calculations it can perform in a second. This is usually measured in Megahertz or Gigahertz — the electrical impulses that power the computer are measured in some form of Hertz (the SI unit of frequency, equal to one cycle per second). For example, 1.5 GHz equates to 1.5 billion cycles per second. This is a frequency rating, of the number of times the event happens electronically in a wave.

The speed of a CPU is usually measured in "clock speed". This is a measure of the number of cycles a CPU executes per second, measured in GHz (gigahertz). During each cycle, billions of transistors within the processor open and close. For example, a CPU with a clock speed of 3.2 GHz executes 3.2 billion cycles per second. A cycle might include the execution of one or multiple instructions, or a single instruction might be handled over multiple clock cycles.

How important is the CPU?

There is no way to run a computer, phone, tablet, etc., without a CPU. Its ability to process external information is integral to the device's functioning. It is one of the most important parts of a computer and makes the decisions for all the other processors a computer, phone, or tablet uses to run apps.

The CPU is vitally important in the functioning of apps, such as gaming, where the CPU sets the frame rate for gameplay. Some systems can overclock. This is when the clock speed of the CPU, which is the top speed in Giga Hertz of the processor, is exceeded.

Many CPUs can overclock, but the act does cause damage to the CPU itself.

What makes a good CPU?

CPUs come in a variety of sizes; smaller processors perform fewer calculations per second but may be better at performing more specific tasks. Single-purpose central processing units, such as those found in smartphones, are small and powerful but not as powerful as their larger cousins in desktop computer central processing units. It all depends on the processor's specifications. There are no such things as good or bad CPUs.

For desktops, there are two leading manufacturers, Intel and AMD. Both are considered to be makers of high-quality, high-performance CPUs.

In the case of smaller, more specialized computers for such industries as communications and healthcare and many others, there are smaller chips designed for completing specific tasks. Again, these are not considered good or bad chips; they are designed to perform in specific roles that may not require very high clock speeds.

CPU specifications

CPU: Here's what to know about the heart and mind of computer-based devices
The CPU installation.

When a CPU runs, it calculates at a certain speed. This speed depends a great deal on the cores that are layered inside the processor housing, one on top of the other.

Some processors have four cores, and some have two, but you need at least two cores to have a processor. The most current processors for desktop computers have 6 or 12 cores and also include a graphics processor within those cores.

CPUs run from 1.5 GHz to 4.2 GHz, and the speeds increase with each new miniaturization of the electronics within the cores, allowing more cores to fit in the same space as a larger core.

The Central Processing Unit may evolve over time, particularly as quantum computers become more common. Even in the amazing world of future computing, the CPU will always be required.