Central processing unit

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A Pentium CPU inside a computer

A central processing unit (CPU) is an important part of almost every computer. The CPU sends signals to control the other parts of the computer, almost like how a brain controls a body.

The CPU is an electronic machine that works on a list of things to do, called 'instructions'. It reads the list of instructions, one instruction at a time, and does each one in order. A list of instructions that a CPU can read is a computer program. A machine that can perform the job of a CPU is often called a Turing machine by mathematicians.

The speed that a CPU works at is measured in "Hertz", "Hz", however modern processors run so fast that "Gigahertz", "GHz", is used. One gigahertz is one billion hertz.

The CPU market is controlled by two companies, Intel and Advanced Micro Devices (usually shortened to AMD). There are other CPU manufacturers like VIA, MCST, ELVEES, SRISA, NTC Module, Sun Microsystems and others, but those companies have very limited users, their processors have a very specific (including military) application or too low in performance.

Types of CPUs[change | change source]

AMD Athlon 64, a 64-bit CPU

There are two different types of CPUs. There is a 32-bit CPU and there is a 64-bit CPU. The main difference between these two processors is the structure. The older processor which is the 32-bit processor has a structure that can process instructions less efficiently than a 64-bit Processor can. Also, a 32-bit processor can handle less instructions at one time than a 64-bit processor can. The more bits, the more that processor can handle and, since 64-bits is larger than 32-bits, that means that a 64-bit processor is the better choice as it can handle more instructions in one load. Moreover, a 32-bit processor can only handle 4GB of RAM (unless using extensions such as Intel's Physical Address Extension), compared to a 64-bit processor which can handle up to 16EB (16 billion GB, or 16 billion billion bytes) of RAM. Now, the amount of memory that a processor can handle does not only depend on the processor, but it also depends on the Operating System of the machine. For example, a Windows 7 Starter Edition OS with a 64-bit processor can only handle 8GB of memory. Compare that to Windows 7 Ultimate with a 64-bit processor which can handle 192GB of memory.

Even though a 32-bit processor can handle up to 4GB of memory, having that much memory on a 32-bit processor will not make it perform quicker.

Functionality[change | change source]

Here are some of the basic things a CPU can do:

  • Add one number with another
  • Test to see if one number is bigger than another
  • Move a number from one place to another
  • Get a number from memory
  • Jump to another place in the instruction list
  • Execute Commands

Even very complicated programs can be made by combining many simple instructions like these. This is possible because each instruction takes a very short time to happen. Many CPUs today can do more than 1 billion (1,000,000,000) instructions in a single second. In general, the more a CPU can do in a given time, the faster it is. One way to measure a processor's speed is MIPS. Flops and CPU clock speed (usually measured in gigahertz) are also ways to measure how much work a processor can do in a certain time.

A CPU is built out of logic gates; it has no moving parts. The CPU of a computer is connected electronically to other parts of the computer, like the video card, or the BIOS. A computer program can control these peripherals by reading or writing numbers to special places in the computer's memory.

Multiple Cores[change | change source]

Some newer processors have "Multiple Cores". This means that they have many processors built on to the same chip so that they can do more than one thing at once.

While the individual cores might be slower than a single core processor, all the cores can work together to go faster. This means that the GHz might be lower, however the overall speed of the processor will be higher.

To make an analogy, think of Traffic lanes;

  • One road having one lane, which takes up 50 cars in 10 minutes.
  • And another road having two lanes, This will take 25 cars in the same 10 minutes and if one of the lanes has a problems cars can go to the other lane.

In today's modern computers, some processors may have up to eight-cores and are available to all consumers, like the AMD FX-8350.

Manufacturers[change | change source]

The following companies make computer CPUs:

Further information[change | change source]