The central processing unit (CPU) is the computer component that's responsible for interpreting and executing most of the commands from the computer's other hardware and software. All sorts of devices use a CPU, including desktop, laptop, and tablet computers, smartphones, even your flat-screen television set.
Intel and AMD are the two most popular CPU manufacturers for desktops, laptops, and servers, while Apple, NVIDIA, and Qualcomm are big smartphone and tablet CPU makers.
You may see many different names used to describe the CPU, including processor, computer processor, microprocessor, central processor, and "the brains of the computer."
Some devices use a single-core processor while others may have a dual-core (or quad-core, etc.) processor. Running two processor units working side-by-side means that the CPU can simultaneously manage twice the instructions every second, drastically improving performance.
Some CPUs can virtualize two cores for every one physical core that's available, a technique known as Hyper-Threading. Virtualizing means that a CPU with only four cores can function as if it has eight, with the additional virtual CPU cores referred to as separate threads. Physical cores, though, do perform better than virtual ones.
CPU permitting, some applications can use what's called multithreading. If a thread is understood as a single piece of a computer process, then using multiple threads in a single CPU core means more instructions can be understood and processed at once. Some software can take advantage of this feature on more than one CPU core, which means that even more instructions can be processed simultaneously.
Just as you'd probably suspect from their naming, Intel Core i7 chips perform better than i5 chips, which perform better than i3 chips. Why one performs better or worse than others is a bit more complex but still pretty easy to understand.
Intel Core i3 processors are dual-core processors, while i5 and i7 chips are quad-core.
Turbo Boost is a feature in i5 and i7 chips that enables the processor to increase its clock speed past its base speed, like from 3.0 GHz to 3.5 GHz, whenever it needs to. Intel Core i3 chips don't have this capability. Processor models ending in "K" can be overclocked, which means this additional clock speed can be forced and utilized all the time; learn more about why you'd overclock your computer.
Hyper-Threading enables the two threads to be processed per each CPU core. This means i3 processors with Hyper-Threading support just four simultaneous threads (since they're dual-core processors). Intel Core i5 processors don't support Hyper-Threading, which means they, too, can work with four threads at the same time. i7 processors, however, do support this technology, and therefore (being quad-core) can process 8 threads at the same time.
Due to the power constraints inherent in devices that don't have a continuous supply of power (battery-powered products like smartphones, tablets, etc.), their processors—regardless if they're i3, i5, or i7—differ from desktop CPUs in that they have to find a balance between performance and power consumption.
Another component of a CPU is cache. CPU cache is like a temporary holding place for commonly used data. Instead of calling on RAM (Random Access Memory) for these items, the CPU determines what data you seem to keep using, assumes you'll want to keep using it, and stores it in the cache. Cache is faster than using RAM because it's a physical part of the processor; more cache means more space for holding such information.
Whether your computer can run a 32-bit or 64-bit operating system depends on the size of data units that the CPU can handle. More memory can be accessed at once and in larger pieces with a 64-bit processor than a 32-bit one, which is why operating systems and applications that are 64-bit-specific cannot run on a 32-bit processor.
Beyond the standard processors available in commercial computers, quantum processors are being developed for quantum computers using the science behind quantum mechanics.
Each motherboard supports only a certain range of CPU types, so always check with your motherboard manufacturer before making a purchase. CPUs aren't always perfect, by the way. Some CPUs can have serious problems.
Intel and AMD are the two most popular CPU manufacturers for desktops, laptops, and servers, while Apple, NVIDIA, and Qualcomm are big smartphone and tablet CPU makers.
You may see many different names used to describe the CPU, including processor, computer processor, microprocessor, central processor, and "the brains of the computer."
What a CPU looks like and Where It's Located
A modern CPU is usually small and square, with many short, rounded, metallic connectors on its underside. Some older CPUs have pins instead of metallic connectors.
The CPU attaches directly to a CPU "socket" (or sometimes a "slot") on the motherboard. The CPU is inserted into the socket pin-side-down, and a small lever helps to secure the processor.
After running even a short while, modern CPUs can get very hot. To help dissipate this heat, it's almost always necessary to attach a heat sink and a fan directly on top of the CPU. Typically, these come bundled with a CPU purchase.
IMPORTANT: Not all CPUs have pins on their bottom sides, but in the ones that do, the pins are easily bent. Take great care when handling, especially when you're installing them onto the motherboard.
A modern CPU is usually small and square, with many short, rounded, metallic connectors on its underside. Some older CPUs have pins instead of metallic connectors.
The CPU attaches directly to a CPU "socket" (or sometimes a "slot") on the motherboard. The CPU is inserted into the socket pin-side-down, and a small lever helps to secure the processor.
After running even a short while, modern CPUs can get very hot. To help dissipate this heat, it's almost always necessary to attach a heat sink and a fan directly on top of the CPU. Typically, these come bundled with a CPU purchase.
IMPORTANT: Not all CPUs have pins on their bottom sides, but in the ones that do, the pins are easily bent. Take great care when handling, especially when you're installing them onto the motherboard.
CPU Clock Speeds
The clock speed of a processor is the number of instructions it can process in any given second, measured in gigahertz (GHz).
For example, a CPU has a clock speed of 1 Hz if it can process one piece of instruction every second. Extrapolating this to a more real-world example: a CPU with a clock speed of 3.0 GHz can process 3 billion instructions each second.
The clock speed of a processor is the number of instructions it can process in any given second, measured in gigahertz (GHz).
For example, a CPU has a clock speed of 1 Hz if it can process one piece of instruction every second. Extrapolating this to a more real-world example: a CPU with a clock speed of 3.0 GHz can process 3 billion instructions each second.
CPU Cores
Some CPUs can virtualize two cores for every one physical core that's available, a technique known as Hyper-Threading. Virtualizing means that a CPU with only four cores can function as if it has eight, with the additional virtual CPU cores referred to as separate threads. Physical cores, though, do perform better than virtual ones.
CPU permitting, some applications can use what's called multithreading. If a thread is understood as a single piece of a computer process, then using multiple threads in a single CPU core means more instructions can be understood and processed at once. Some software can take advantage of this feature on more than one CPU core, which means that even more instructions can be processed simultaneously.
For Example: Intel® Core™ i3 VS Intel® Core™ i5 VS Intel® Core™ i7
For a more specific example of how some CPUs are faster than others, let's look at how Intel has developed its processors.
For a more specific example of how some CPUs are faster than others, let's look at how Intel has developed its processors.
Just as you'd probably suspect from their naming, Intel Core i7 chips perform better than i5 chips, which perform better than i3 chips. Why one performs better or worse than others is a bit more complex but still pretty easy to understand.
Intel Core i3 processors are dual-core processors, while i5 and i7 chips are quad-core.
Turbo Boost is a feature in i5 and i7 chips that enables the processor to increase its clock speed past its base speed, like from 3.0 GHz to 3.5 GHz, whenever it needs to. Intel Core i3 chips don't have this capability. Processor models ending in "K" can be overclocked, which means this additional clock speed can be forced and utilized all the time; learn more about why you'd overclock your computer.
Hyper-Threading enables the two threads to be processed per each CPU core. This means i3 processors with Hyper-Threading support just four simultaneous threads (since they're dual-core processors). Intel Core i5 processors don't support Hyper-Threading, which means they, too, can work with four threads at the same time. i7 processors, however, do support this technology, and therefore (being quad-core) can process 8 threads at the same time.
Due to the power constraints inherent in devices that don't have a continuous supply of power (battery-powered products like smartphones, tablets, etc.), their processors—regardless if they're i3, i5, or i7—differ from desktop CPUs in that they have to find a balance between performance and power consumption.
More Information
Neither clock speed, nor simply the number of CPU cores, is the sole factor determining whether one CPU is "better" than another. It often depends most on the type of software that runs on the computer—in other words, the applications that will be using the CPU.
One CPU may have a low clock speed but is a quad-core processor, while another has a high clock speed but is only a dual-core processor. Deciding which CPU would outperform the other, again, depends entirely on what the CPU is being used for.
For example, a CPU-demanding video editing program that functions best with several CPU cores is going to work better on a multicore processor with low clock speeds than it would on a single-core CPU with high clock speeds. Not all software, games, and so on can even take advantage of more than just one or two cores, making any more available CPU cores pretty useless.
Neither clock speed, nor simply the number of CPU cores, is the sole factor determining whether one CPU is "better" than another. It often depends most on the type of software that runs on the computer—in other words, the applications that will be using the CPU.
One CPU may have a low clock speed but is a quad-core processor, while another has a high clock speed but is only a dual-core processor. Deciding which CPU would outperform the other, again, depends entirely on what the CPU is being used for.
For example, a CPU-demanding video editing program that functions best with several CPU cores is going to work better on a multicore processor with low clock speeds than it would on a single-core CPU with high clock speeds. Not all software, games, and so on can even take advantage of more than just one or two cores, making any more available CPU cores pretty useless.
Another component of a CPU is cache. CPU cache is like a temporary holding place for commonly used data. Instead of calling on RAM (Random Access Memory) for these items, the CPU determines what data you seem to keep using, assumes you'll want to keep using it, and stores it in the cache. Cache is faster than using RAM because it's a physical part of the processor; more cache means more space for holding such information.
Whether your computer can run a 32-bit or 64-bit operating system depends on the size of data units that the CPU can handle. More memory can be accessed at once and in larger pieces with a 64-bit processor than a 32-bit one, which is why operating systems and applications that are 64-bit-specific cannot run on a 32-bit processor.
Beyond the standard processors available in commercial computers, quantum processors are being developed for quantum computers using the science behind quantum mechanics.
Each motherboard supports only a certain range of CPU types, so always check with your motherboard manufacturer before making a purchase. CPUs aren't always perfect, by the way. Some CPUs can have serious problems.
Manufacturing
While the way CPUs work may seem like magic, it’s the result of decades of clever engineering. As transistors—the building blocks of any microchip—shrink to microscopic scales, the way they are produced grows ever more complicated.
Photolithography
Transistors are now so impossibly small that manufacturers can’t build them using normal methods. While precision lathes and even 3D printers can make incredibly intricate creations, they usually top out at micrometer levels of precision (that’s about one thirty-thousandth of an inch) and aren’t suitable for the nanometer scales at which today’s chips are built.
Photolithography solves this issue by removing the need to move complicated machinery around very precisely. Instead, it uses light to etch an image onto the chip—like a vintage overhead projector you might find in classrooms, but in reverse, scaling the stencil down to the desired precision.
The image is projected onto a silicon wafer, which is machined to very high precision in controlled laboratories, as any single speck of dust on the wafer could mean losing out on thousands of dollars. The wafer is coated with a material called a photoresist, which responds to the light and is washed away, leaving an etching of the CPU that can be filled in with copper or doped to form transistors. This process is then repeated many times, building up the CPU much like a 3D printer would build up layers of plastic.
It doesn’t matter if you can make the transistors smaller if they don’t actually work, and nano-scale tech runs into a lot of issues with physics. Transistors are supposed to stop the flow of electricity when they’re off, but they’re becoming so small that electrons can flow right through them. This is called quantum tunneling and is a massive problem for silicon engineers.
Defects are another problem. Even photolithography has a cap on its precision. It’s analogous to a blurry image from the projector; it’s not quite as clear when blown up or shrunk down. Currently, foundries are trying to mitigate this effect by using “extreme” ultraviolet light, a much higher wavelength than humans can perceive, using lasers in a vacuum chamber. But the problem will persist as the size gets smaller.
Defects can sometimes be mitigated with a process called binning—if the defect hits a CPU core, that core is disabled, and the chip is sold as a lower end part. In fact, most lineups of CPUs are manufactured using the same blueprint, but have cores disabled and sold at a lower price. If the defect hits the cache or another essential component, that chip may have to be thrown out, resulting in a lower yield and more expensive prices. Newer process nodes, like 7nm and 10nm, will have higher defect rates and will be more expensive as a result.
Packing It Up
Packaging the CPU for consumer use is more than just putting it in a box with some styrofoam. When a CPU is finished, it’s still useless unless it can connect to the rest of the system. The “packaging” process refers to the method where the delicate silicon die is attached to the PCB most people think of as the “CPU.”
This process requires a lot of precision, but not as much as the previous steps. The CPU die is mounted to a silicon board, and electrical connections are run to all of the pins that make contact with the motherboard. Modern CPUs can have thousands of pins, with the high-end AMD Threadripper having 4094 of them.
Since the CPU produces a lot of heat, and should also be protected from the front, an “integrated heat spreader” is mounted to the top. This makes contact with the die and transfers heat to a cooler that is mounted on top. For some enthusiasts, the thermal paste used to make this connection isn’t good enough, which results in people delidding their processors to apply a more premium solution.
Once it’s all put together, it can be packaged into actual boxes, ready to hit the shelves and be slotted into your future computer. With how complex the manufacturing is, it’s a wonder most CPUs are only a couple hundred dollars.
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