Understanding the Central Processing Unit

Understanding the Central Processing Unit (CPU): A Beginner’s Guide.

Navigating the world of computer parts can be daunting for the uninitiated. There are many different components like the hard drive, motherboard, RAM, and GPU, each with unique functions and many variations. But arguably, the most crucial component of them all is the CPU.

Play Video about Understanding the Central Processing Unit

Every single computing device has a CPU. You may have heard of this tech term before, but what is it exactly? What is a CPU and how does it work?

In this beginner-friendly article, you’ll learn the basics of what a CPU actually is, and we’ll give you an overview of how it works.

What is a CPU(Central Processing Unit)?

CPU refers to the central processing unit, which is a very large-scale integrated circuit and is the computing core (Core) and control core (Control Unit) of a computer. Its function is mainly to interpret computer instructions and process data in computer software.

The central processing unit mainly includes an arithmetic unit (ALU, Arithmetic Logic Unit), a cache memory (Cache), and a bus (Bus) for realizing data (Data), control, and status between them. It, together with internal memory (Memory) and input/output (I/O) devices, is called the three core components of an electronic computer.

Understanding the Central Processing Unit

What does a CPU(Central Processing Unit) do in a computer?

Just to clarify, any programable machine that automatically carries out logical operations or sequences of arithmetic is a computer. In other words, your laptops, desktops, PC tablets for sale, gaming consoles, and smartphones are all computers. So, what does a CPU do in a computer? Well, it interprets binary signals to complete actions, and calculations, and run applications in a three-step process:

  • Fetch: The CPU fetches instructions from the computer’s memory and stores them in a part of its control unit called the Instruction Register (IR).
  • Decode: The CPU sends the instruction from the IR to its instruction decoder. This combinatorial circuit decodes the instruction into signals.
  • Execute: The decoded signals travel to relevant destinations in the CPU for the execution phase.

A CPU also works with other components. For example, it may take relevant data sent from a video game to a graphics card. The graphics card then processes the information to display on a monitor. Likewise, a CPU helps move data from a computer’s hard drive to its memory for faster access.

What makes a CPU good?

Clock Speed

A clock speed tells you how many instructions a CPU can manage in a second and generally indicates how fast it is. From the 90s to the early 2000s, CPU clock speeds improved significantly with every new generation. However, advancements in clock speeds began to plateau due to extra heat generation and higher power consumption. Here, manufacturers found it more cost-effective to enhance CPUs in other ways, so much so that a modern processor can usually outperform a decade-old processor that has a higher clock speed.

Understanding the Central Processing Unit


The multi-core processor revolution began with dual-cores and quad-cores. Instead of focusing on advancing clock speed, manufacturers fitted multiple CPUs on one chip. Nowadays, premium CPUs are hitting 32 cores, 64 cores, and more. Such CPUs are an excellent choice for video editors, game streamers, and users of demanding applications, though they may be something of an overkill for the average user.


Hyper-threading is a technological innovation from Intel that allows a single processor core to perform like two by dividing workloads for simultaneous processing. To put it crudely, imagine dividing a hot dog into two and eating both pieces together for faster consumption instead of starting on one end and working your way to the other. Of course, Intel’s competitor AMD has its own version of hyper-threading.

CPU(Central Processing Unit) performance

Main frequency

The clock frequency inside the CPU is the operating frequency when the CPU performs calculations. Generally speaking, the higher the main frequency, the more instructions are completed in one clock cycle, and the faster the CPU’s computing speed.
However, due to different internal structures, not all CPUs with the same clock frequency have the same performance.


That is, the system bus, the frequency at which data is transmitted between the CPU and peripheral devices, specifically refers to the bus speed between the CPU and the chipset.

Understanding the Central Processing Unit


In the past, there was no concept of frequency multiplication. The main frequency of the CPU was the same as the speed of the system bus. However, as the speed of the CPU became faster and faster, the frequency multiplication technology was born accordingly. It can make the system bus work at a relatively low frequency, and the CPU speed can be infinitely improved through frequency multiplication.

Then the calculation method of CPU main frequency becomes main frequency = FSB x multiplier. That is, the frequency multiplier refers to the multiple of the difference between the CPU and the system bus. When the external frequency remains unchanged, the higher the frequency multiplier, the higher the CPU’s main frequency.


Most of the data information processed by the CPU is retrieved from the memory, but the computing speed of the CPU is much faster than that of the memory. Therefore, memory is placed during the transmission process to store the data and instructions frequently used by the CPU. This increases data transfer speed. It can be divided into first-level cache and second-level cache.

L1 cache

That is L1 Cache. Integrated into the CPU, it is used for the temporary storage of data during CPU processing. Since the cache instructions and data work at the same frequency as the CPU, the larger the capacity of the L1 cache, the more information is stored, which can reduce the number of data exchanges between the CPU and the memory and improve the computing efficiency of the CPU. However, because the cache memory is composed of static RAM and has a complex structure, the capacity of the L1-level cache cannot be made too large on the limited CPU chip area.

L2 cache

Namely L2 Cache. Due to the limitation of L1 level cache capacity, in order to increase the computing speed of the CPU again, a high-speed memory, that is, a second-level cache is placed outside the CPU. The working frequency is relatively flexible, it can be the same frequency as the CPU, or it can be different. When the CPU reads data, it first looks in L1, then in L2, then in memory, and then in external memory. Therefore, the impact of L2 on the system cannot be ignored.

Memory bus speed

Refers to the speed of data exchange between the CPU(Central Processing Unit) and the second level (L2) cache and memory.

Understanding the Central Processing Unit

Expansion bus speed

Refers to the data transmission speed between the CPU and the expansion device. The expansion bus is the bridge between the CPU and external devices.

Address bus width

Simply put, it is how much memory the CPU can use, and the physical address space that can read data.

Data bus width

The data bus is responsible for the size of the data flow of the entire system, and the width of the data bus determines the amount of information for one data transfer between the CPU and the L2 cache, memory, and input/output devices.

Unmarked pictures come from Internet, and source: … …

A Central Processing Unit or CPU is electronic machinery that carries out instructions from programs that allow a computer or other device to perform its tasks.
The CPU is the brain of a computer, containing all the circuitry needed to process input, store data, and output results. The CPU is constantly following instructions from computer programs that tell it which data to process and how to process it. Without a CPU, we could not run programs on a computer.