CPU Basics: Multiple CPUs, Cores, And Hyper-Threading

What’s a central processing unit (CPU)?
The central processing unit (or CPU) in your computer is the brains of the operation. It’s a small computer chip that sits atop the main circuit board (motherboard) of a computer. It performs the computational work, such as running programs or applications.

It’s the core of your PC, smartphone, or tablet, and it’s what makes the whole device run as it should. At its core, a CPU takes instructions from a program or application and performs a calculation.

The executed instruction, or calculation, can involve basic arithmetic, comparing certain numbers together, or moving them around in memory.

Since everything in a computer is represented by numbers, those kinds of simple tasks equate to what a CPU does. It’s what facilitates everything from starting up Windows to watching a video.

CPU clock speed, or clock rate, is measured in Hertz – generally in gigahertz, or GHz. A CPU’s clock speed rate is a measure of how many clock cycles a CPU can perform per second. The clock speed used to be enough when comparing performance.

Things aren’t so simple anymore.

A CPU core is a CPU’s processor. A core can work on one task while another core works on a different task, so the more cores a CPU has, the more efficient it is.

A CPU that offers multiple cores or hyper-threading may perform significantly better than a single-core CPU of the same speed that doesn’t feature hyper-threading.

PCs with multiple CPUs can have an even bigger advantage.

All of these features are designed to allow PCs to more easily run multiple processes at the same time – increasing your performance when multitasking or under the demands of powerful apps like video encoders and computer aided design (CAD) applications.

What is hyper-threading?
Hyper-Threading (simultaneous multithreading) is a process where a CPU splits each of its physical cores into virtual ones, which are known as threads.

Hyper-threading allows each core to do two things simultaneously. It increases CPU performance by improving the processor’s efficiency, thereby allowing you to run multiple demanding apps at the same time.

Multiple cores
Originally, CPUs had a single core. That meant that the physical CPU had a single central processing unit on it. To increase performance, manufacturers added additional “cores,” or central processing units.
A dual-core CPU has two central processing units, so it appears to the operating system as two CPUs.

A CPU with two cores could run two different processes at the same time. This speeds up your system because your computer can do multiple things at once.

Multiple CPUs
Most computers only have a single CPU. That single CPU may have multiple cores or hyper-threading technology – but it’s still only one physical CPU unit inserted into a single CPU socket on the motherboard.

Before hyper-threading and multi-core CPUs came around, people attempted to add additional processing power to computers by adding additional CPUs. This requires a motherboard with multiple CPU sockets.

The motherboard also needs additional hardware to connect those CPU sockets to the RAM and other resources. Systems with multiple CPUs also consume more power.

Systems with multiple CPUs aren’t very common among home PCs today. Even a high-powered CAD desktop with multiple graphics cards will generally only have a single CPU.

You’ll find multiple CPU systems among supercomputers, servers, and similar high-end systems that need as much number-crunching power as they can get.