Understand computer processors: CPU and vCPU and threads and cores

The central processing unit (CPU) is the brain of our computers. They handle everything we do every day, from opening apps to watching movies. But what exactly is a CPU? How does it work? What is the difference between a CPU and the increasingly popular vCPU?

Understand the computer brain

According to a complete history guide published by G2, the first electronic computers were created in the early 1800s. However, these computers were large and expensive and could only be used by trained mathematicians and scientists.

Charles Babbage is credited with inventing the first computer difference engine, which could be programmed to perform any calculation that could be done manually. However, the difference engine project was never completed due to lack of funding, according to the Computer History Museum.

In 1937, Babbage first mentioned the analytical machine, which would become the world's first general-purpose mechanical computer. "An analysis engine contains all the elements of a modern computer: arithmetic logic units, conditional branches and control flow in circular form, and integrated memory," he said.

A key component of today's computers is the CPU, or central processing unit. The CPU is responsible for executing the instructions given to it by software such as the operating system or applications. In layman's terms, you can think of the CPU as the brain of your computer. The CPU consists of two main parts: the control unit and the arithmetic logic Unit (ALU). If these abbreviations confuse you, see our overview of how APUs, cpus, and Gpus are different.

Understand computer processors: CPU and vCPU and threads and cores

The control unit is responsible for fetching instructions from memory, decoding them, and sending them to the arithmetic logic unit for execution. The ALU performs arithmetic and logical operations on data stored in registers, which are the storage units within the CPU.

Modern cpus also contain a cache, which is a small amount of high-speed memory used to store frequently used instructions and data. The cache is classified into levels; Level 1 (L1) caches are built into the CPU chip itself, level 2 (L2) caches are located on a separate chip close to the CPU, and level 3 (L3) caches are located on a chip further away from the CPU, even on its own circuit board on its own chip.

CPU and vCPU

With the rise of cloud services, the emergence of virtual central processing units, or Vcpus. TechTarget defines a vCPU as "the physical central processing unit (CPU) assigned to a virtual machine (VM)."

Virtual machines are basically separate operating systems that run in another operating system as if they were applications. VMS are used for a variety of purposes, such as testing new software in a secure environment, running multiple operating systems (such as Windows and Linux) on the same computer, or consolidating multiple physical servers into a single server to save space and reduce costs.

Therefore, vCPU is the software implementation of CPU; It doesn't actually exist on your computer like a real CPU. A hypervisor is software that creates and manages VMS and allocates Vcpus to virtual machines. The operating system within the VM treats each vCPU as a true CPU core. See our explanation of virtual Machine hypervisors for more information.

However, because Vcpus are software-based, they are not as efficient as real cpus. Therefore, it is important to specify the number of processor cores when purchasing a computer (for example, "quad-core" means four cores). The same rules apply when selecting a virtual private Server (VPS) or dedicated server hosting plan.

The main difference between cpus and Vcpus is that cpus are hardware-based while Vcpus are software-based. This means that the CPU physically exists on your computer, while the vCPU does not; Instead, they are created by the hypervisor as needed. Because of this difference in implementation, cpus are more efficient than Vcpus; They have no overhead associated with running in software.

Since the early 2000s, Vcpus have become increasingly popular because they are cheaper and easier to distribute than physical cpus; However, if you are looking for performance, it is best to use a computer with multiple CPU cores, because each core can process instructions independently.

Core and Thread

A CPU may have one or more cores, which are processing units that perform tasks at specified times. The kernel maintains the task execution order, registers, and caches, if applicable, and performs operations through the ALU. The CPU controls the kernel, but the kernel executes every software process or thread scheduled by the operating system. A thread is a separate sequence of instructions that can be processed by the CPU.

Multiple threads can exist in the same process and share the same memory space. This allows them to communicate with each other more easily than if they were running in a separate process. Threads are commonly used to improve the performance of multithreaded applications by allowing different parts of the program to run simultaneously on different kernels or processors.

The word "thread" has been used in computing terms for many years. However, it wasn't until the early 2000s that processors introduced hardware-level support for threads. This allows multiple threads to execute simultaneously on different kernels. Previously, no matter how many cores there were in the processor, only one thread could be executed on a single kernel at a time. Multicore processors are now common, and most operating systems provide some degree of support for running programs with multiple threads.

Summarize the core issues

In summary, cpus are the hardware-based brains of our computers, and their virtual counterparts, vcpus, are software-based, created by hypervisors to run in virtual machines. The kernel is the hardware-based processing unit of the CPU, while threads are software-based instructions that the CPU can process.

Threads can be executed simultaneously on different kernels, which allows different parts of the program to run simultaneously. This improves hardware performance because multiple tasks can be processed simultaneously rather than sequentially.

Now that you know the difference between CPU, vCPU, kernel, and thread, you can make an informed decision when choosing a computer or server. If you're looking for performance, it's best to choose a computer with multiple CPU cores, because each core can process instructions independently. However, if you are looking for a cost-effective solution, vCPU may be your best choice.

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