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What is a CPU? CPUs Explained!

Posted by Josh Fewell on Aug 21st 2020

What is a CPU? CPUs Explained!

What is a CPU?

What is a processor? What is a CPU? Computer processors are referred to in multiple ways. The abbreviation, CPU, stands for ‘Central Processing Unit’, and its role is crucial to the performance of your computer. So, what exactly is a processor?

Central Processing Unit

The CPU is a piece of hardware that performs basic logic, arithmetic, controls, and I/O (input/output) operations. It is often referred to as “the brain of the computer” because it functions as the main control center for all computer operations. Before we get into the operation of a processor, we need to first understand the language in which computer parts communicate. 

Data

The information that your hardware passes back and forth is called data. As complex as your data can be, there are only 2 characters in your computers alphabet; 1 and 0. 1 and 0 can mean any binary statement, such as: true or false, on or off, yes or no. Each of these characters is called a bit.

The language in which these characters are used is called binary. You might be wondering how you can run a whole computer on just 2 characters your CPU understands. Well, when you group 8 bits together, you get what is called a byte. With 8 digits, you run into a wide variety of combinations.

For example, the lowercase letter ‘a’ can be translated to ‘01100001’. And the word ‘apple’ is translated to ‘01100001 01110000 01110000 01101100 01100101’. These are very simple letters and words, but your CPU deals with much more complicated strings of binary that contain complex instructions and locations of data throughout your system. 

Operation

The most basic operation of processors is to execute commands that are called for in a program. These commands are stored in your system RAM (ref. https://centralvalleycomputerparts.com/articles/-ram-explained/). The three basic steps of operation are: Fetch, Decode, and Execute. This is called the ‘Instruction Cycle’.

In Short, the instruction is fetched from the RAM by the CPU, decoded, and then the procedure is executed.

what is a cpu

Fetch

This step begins with the CPU receiving an instruction. The instruction is presented as a string of binary. It has a unique location (also written in binary) which is referred to as the ‘address’, which is in the program memory.

Decode

When the instruction is received into the instruction decoder and converted into signals that the other parts of the CPU can read. Each CPU has its own instruction set architecture or ISA. The processor’s ISA determines the way that the instruction is interpreted. This is where basic actions are performed billions of times per second (like adding two numbers together or comparing data).

Execute

After the instruction is fetched and decoded, it can be executed. This is where basic actions are performed billions of times per second (like adding two numbers together or comparing data). This can either be a single action or an entire sequence of actions, and when performed, is logged on an internal CPU register so that later instructions can reference back to prior outcomes. For example, if you were adding two numbers together, it would save the sum because a future instruction may be to display the sum on your monitor.

There is much more to be said about the function of computer processors, but for the sake of understanding, this should be a simple and comprehensible example.

Sockets

CPUs are attached to a motherboard via a CPU Socket. There are 3 common sockets: Land Grid Array (LGA), Pin Grid Array (PGA), and Ball Grid Array (BGA).

LGA processors have hundreds or thousands of flat, gold contacts on the bottom of the CPU that are placed onto pins in the motherboard socket and then clamped down via a metal bracket. LGA processors are typically used in desktop systems for personal use and in most modern servers as well. Although, this is not always the case as each type can be used for multiple purposes.

PGA processors have a large quantity of conductive pins that slide down into a socket with holes for each pin. These are held down in a similar way to LGA processors.

BGA processors are intended to be permanently mounted to a motherboard. They have pads on the bottom with a tiny ball of solder that is heated to melt and fuse to a motherboard.

Speed

Speed of a CPU is measured in gigahertz (GHz). This measurement is often referred to as your CPU Clock Speed and is generally used to gauge processor power. The clock speed measures how many cycles your CPU executes in a second (GHz per second). The clock of your CPU has a constant tempo that cycles billions of times per second. For example, if your CPU is 2.5GHz, it executes 2.5 billion cycles per second. Sometimes it takes one cycle to complete one instruction, but that is not always true because not all instructions are the same size.

CPU Cores/Threads

A multicore processor has, essentially, multiple processors built into one. Each CPU core in your can complete its own cycles and instructions. So, the more cores you have the more your computer will be able to multitask. Threads are similar to this, if your CPU is multithreaded, your CPU cores are able to function on multiple instructions within themselves.

If you still find yourself wondering, "What is a CPU?", here's some links to some resources I found helpful. We publish regular content here at CVCP and would love to cover any subject you find interesting, so be sure to contact us to let us know what to write about! Here's an article that details CPU specifications!

SOURCES:

https://computerscience.chemeketa.edu/

https://www.intel.com/content/www/us/en/gaming/resources/cpu-clock-speed.html#:~:text=If%20you're%20wondering%20how,be%20listed%20under%20%E2%80%9CProcessor%E2%80%9D.