What Is a CPU/Processor?

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What Is a CPU/Processor?

If a computer is like a human body, then the monitors are the eyes, the keyboard and mouse are the fingers and other sensory inputs, and the central processing unit (CPU) is the brain. Without the innards within the desktop or laptop, the computer would just be a zombie-like husk. Just as there are many types of computers, there are many types of CPU. Whether buyers intend to purchase a new computer or want to upgrade an existing computer with a new CPU, there are many variables to consider.

To get a better understanding of what a CPU is, computers can be examined from the inside out, taking into account the features and different manufacturers of CPUs. There are many places to look for CPUs including specialist computer shops and large electronics retailers. When shopping online, eBay is the best place to look. The site has an incredible selection of products, which can often be purchased at significantly less than the retail price.

How a CPU Works

The good news about a CPU is that it is easier to explain how it works compared to the human brain. A CPU takes instructions from the various input devices of the computer and performs a variety of functions. These functions fall into three main categories: mathematical functions through the arithmetic logic unit (ALU), moving memory from one location to another, and jumping to new sets of instructions based on a decision tree.

Basic Components of a CPU

The following table lists the basic components of a simple processor. Most CPUs are much more sophisticated and have many more parts, but these are the most common features.

Component of a CPU


Address bus

Sends an address to memory

Can be 8, 16, or 32 bits wide

Data bus

Sends or receives data to or from memory

Can be 8, 16, or 32 bits wide

Read and write lines

Alerts memory to whether the data is set or get to the addressed location

Clock line

Sequences the processor via a clock pulse

Reset line

Restarts execution and resets program counter to a specific number, often zero

All CPUs have these basic components. These parts access the memory, which is the main part of the CPU.


There are two types of memory: read-only memory (ROM) and random-access memory (RAM). Each type is constructed differently and functions in a particular way.


Also known as firmware, ROM is found on an integrated circuit that is used in all kinds of electronic items. Data stored on ROM chips is not lost when there is no longer power, and it requires a special operation to change. When diodes intersect on the ROM chip, the value is one. When the diodes do not intersect, the value is zero.


RAM is the most well known form of computer memory. RAM chips have a transistor and a capacitor that combine to create a single bit of data, which is called a memory cell. A transistor on the chip provides a switch so that the memory can be read or changed. When the power goes off, RAM goes off as well.

Key Features of a CPU

Once a user understands the basics of the how the CPU works and how it interacts with the rest of the computer, the next step is to look at the key features of the unit. These features are the number of cores, socket type, and clock speed.

Number of Cores of a CPU

One common way to describe a CPU is to state how many execution cores it has. Most advanced chips have eight cores. Each core allows the computer to do an added operation simultaneously, but it does not necessary allow each operation to work faster. The more cores the computer has, the less it slows down when multiple operations are happening at the same time. In other words, more cores result in greater processing capabilities, but possibly no effect on overall speed.

Socket Type of a CPU

The CPU socket is the component that provides connections between a processor and a printed circuit board (PCB). Sockets allow the CPU to be replaced without soldering. They usually have a retention clip that applies a constant force that must be overcome when the CPU is inserted. Chips that have a lot of pins either use a zero insertion force (ZIF) or land grid array (LGA) socket. CPU sockets are generally not used in laptops because space is limited. They are often used for prototyping new circuits.

Clock Rate of a CPU

Clock rate is also known as clock speed or clock cycles. This measure described how many cycles per second a processor can run through. The more cycles, the faster the processor can receive a charge of electricity. Most chips operate at numbers in the billions of cycles per second. This is most often expressed in gigahertz. CPUs also have variable bit widths. This is the number of bits of information that can be transferred at the same time. Larger bit widths and clock speed result in greater processing capabilities and computer speed.

Multiprocessor Computers

For the most processing power, users can get a computer that runs more than one CPU at the same time. These computers are often servers used in applications. The CPUs may all be the same or there may be some that are dedicated to specific tasks. Systems that treat all CPUs the same are called symmetric multiprocessing (SMP) systems. Multiprocessing requires special operating system software and hardware to be incorporated into a computer system.

Manufacturers of CPUs

There are a number of smaller manufacturers of CPUs, but Intel and AMD dominate the market. Other names to consider are Cyrix, IBM, and Texas Instruments. Apple uses Motorola chips in its Macintosh CPUs.


Intel began in 1968 and introduced the first microprocessor in 1971. The company is headquartered in Santa Clara, California, USA and the office in the United Kingdom is in Swindon. Nearly 45 percent of the company's employees live outside of the United States. Intel CPUs are among the most well known and most reliable in the industry.

Intel Pentium Processor

Pentium is by far the most well known of CPUs. The name is derived from the Greek word penta, which means five because the chips used Intel's fifth-generation microarchitecture. The Pentium was introduced in 1993 and has a clock speed range of 60 MHz to 3.8 GHz. Many of Intel's other processors have been folded into the Pentium brand over the years. Pentium-compatible is used to describe any processor that supports the IA-32 instruction set and architecture.

Intel Celeron Processor

Celeron is one of the older CPUs made by Intel. It was introduced in 1998 and based on the Pentium II branded core. Celeron processors often have less cache memory or have advanced features disabled deliberately. The clock rate on Celeron processors ranges from 266 MHz to 3.6 GHz.

Intel Core 2 Processor

The Core 2 was debuted by Intel in 2006. Its clock rate goes from 1.06 to 3.5 GHz. There are a number of varieties of the Core 2, including the single-core Solo, dual-core Duo, quad-core Quad, and the Extreme, introduced in 2007 for dual and quad-core systems. The Core 2 is often known as C2.

Intel Xeon Processor

Intel also offers a multiprocessing CPU called the Xeon, which was introduced in 1998. It has a clock rate range of 400 MHz to 4.4 GHZ. The Xeon is generally targeted at workstations, servers, and embedded system markets for non-consumer computers. Supercomputers that use Xeon processors have been rated among the fastest in the world.


AMD (Advanced Micro Devices) is the second largest developer of CPUs and the largest supplier of graphics processing units; it produces more than NVIDIA. AMD was founded in 1969, just a year after Intel.

AMD Athlon 64 Processor

The Athlon 64 was released to the public in 2003 and has a maximum clock rate of 1.0 to 3.2 GHz. It was the successor to the Athlon XP and the third processor to be named Athlon. It is backward compatible to 32-bit computers, despite being native to 64-bit systems. There are both single and dual-core versions of the Athlon 64.

AMD Sempron Processor

Sempron is the name of the value processor made by Athlon. The series has used various technologies and CPU socket formats. The maximum clock rate ranges from 1.0 to 2.9 GHz and the Sempron was debuted in 2004. Sempron replaced the Duron made by Athlon and is competitive with the Intel Celeron processor.

AMD Turion 64 Processor

The Turion 64 was once called Mobile Athlon 64. It is the brand name that applies to lower consumption, 64-bit processors. Models are compatible with Socket S1 and have 64-bit single channel on-die memory controller, and an 800 MHz HyperTransport bus. They also have a number of battery saving functions.

AMD Opteron Processor

For servers and workstations, Athlon provides the Opteron with a maximum clock rate range of 1.4 to 3.3 GHz. The Opteron was introduced in 2003 and was intended to compete with Intel's Xeon. Like the Xeon, Opteron has been used in supercomputers such as those used at Oak Ridge National Laboratory and the IBM Roadrunner at Los Alamos National Laboratory.

How to Buy CPUs on eBay

While finding the CPU in a computer may not be easy as a beginner, it is not hard to find CPUs on eBay. The site's search engine can be accessed via the text box found on almost every page. Simply type "CPU" and you are given a large number of results. To narrow your results, you can add terms, such as the specifics of the CPU, the manufacturer's name, or the brand name of the processor.

Researching Sellers on eBay

When you are searching for a CPU, you should make sure that the seller is reputable. Every product page has seller information, including the seller's username and feedback rate. By clicking on the username, you are given more details, including specific comments from past buyers and ratings for communication, dispatch time, and item description accuracy. You can also look at all of the seller's listings via his or her seller page.


When purchasing a computer, buyers should pay attention to the internal components and not just the bells and whistles on the exterior. The most important part of the computer is the CPU because it determines how quickly the machine runs. Whether buying a new desktop PC or just a CPU chip, buyers should be aware of the number of cores, the socket type, and the clock rate. These determine how many processes the computer can run simultaneously and how quickly the computer can run each process.

The main manufacturers of CPUs are Intel and AMD, and buyers can choose similar units from each company. However, the specifics of each processor should be researched in order to select the most appropriate type. Buyers can find a wide range of CPUs on eBay. The site provides details for each product and buyers can also research sellers and often save a nice amount of money.

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