CPU the easy way – Part 2 (CPU basics)

In Part I of this series we learned about the Von Neumann architecture.
Let’s dig a bit deeper and learn how this is all glued together.
So what is really a CPU and what does it look like?

CPU stands for “central processing unit” and we think of it as the brain of the computer. It is an electronic brain that is general and that means that it can do extremely simple tasks. What you see on the right side is a modern CPU that you will find in a lot of the computers out there. As with cars the CPUs also come in different sizes, shapes, color, performance and they are made by different companies.
Examples of the simple tasks that the CPU can do:

  • Take one number and add that number with another one (2 + 2 = 4)
  • Compare two numbers
  • Check if a number is positive (larger than zero)

As we learned in the first part we know that inside of this electronic brain we find some parts.

  • Arithmetic/Logic Unit which we refer to as ALU is the one who is actually doing the math inside the CPU such as the examples above. He’s the smart guy!
  • Control Unit is the one who is coordinating all of the activities inside of the CPU. To make it easier you could think of the Control Unit as the ALU’s secretary.
  • Register Unit which is a temporary data storage location which has many cells that are uniquely addressed just like seats inside of a cinema. We need those cells for storing the things that we want ALU to do, as well as the things that this smart guy has completed, namely the results. But just temporary because ALU and Control Unit has a lot do to and the Register Unit has limited space in it’s warehouse.

These are the three main parts inside of the CPU. I know I mentioned some others in the last part of this series when we learned about the Von Neumann architecture, we will soon find out what they do too, but for now let’s focus on the CPU only.
Summary so far:
ALU is the smart guy doing all the basic math, Control Unit is the secretary running around coordinating all the activities and the Register Unit is the temporary warehouse where things are stored in uniquely addressed cells.Basic-CPU
I mentioned that these cells inside of the Register Unit is uniquely addresses. The reason for this is that the Control Unit (the secretary) is telling the ALU (the smart guy) which cells have the numbers it should work on.
The Control Unit (secretary) tells ALU (smart guy)
“Please go to seat 5 and seat 9 inside of the cinema and collect the numbers you find. Once you have done your calculation job – please leave the result in seat 12 so I know where to find it”
I mentioned that the ALU can do extremely simple math, but it can do so extremely fast!
So far we know the basic parts inside of the CPU, and in the next part we will dig deeper and see how the CPU communicates with the computer’s memory, and this is where the Von Neumann architecture comes into play.
Continue to Part 3

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