The CPU is the “central processing unit” in a computer. This term applies both to the box bit in a desktop computer and also the chip that lies at the heart of that piece of equipment. The chip is also referred to as the “IC” which stands for “integrated chip.” It is also called the processor, or micro-processor. The processor is the thinking bit of the computer. Everything else inside the box is a peripheral to that – the hard drive, communication and USB ports, for example. Some computers work faster than others, but to understand why you need to understand how a CPU works.
The CPU is pinned onto a motherboard. Electricity moves over metal tracks printed onto the board. The inside of the CPU is exactly the same, but scaled down to microscopic dimensions. A row of pins either side of the processor make it look a little like a beetle. These pins connect to the metal tracks on the motherboard and transfer the electricity onto the thin metal tracks inside the processor. The main components inside the processor are an area of memory storage and a series of registers. Registers are like a row of dials like the display of a meter. These registers, however, can each only have the value of 0 or 1 and it is the adding together of binary numbers in the registers that make the computer “think.”
The metal tracks that transport electricity around the motherboard and the processor combine together as a “bus.” Computers work with binary numbers. Binary digits can only be 0 or 1, which are represented by a high voltage or a low voltage. Each digit in a binary number is called a bit. Eight bits make a byte. The bus contains eight tracks and the eight bits in a byte travel together each on a different tack. Newer computers are designed to carry more than one byte by having more tracks. You can have 64 bits travelling along together in a computer, which is eight bytes all at once.
The speed of a computer is the number of bytes that can be shifted around in a second. Each device inside the computer needs to know when one bit starts and the next one ends. For example, image if three bits are sent down a track one after the other, each forming part of three different bytes of data. The first byte contains a 1 on that track, the second also contains a 1 and so does the third. So the receiving component gets 111 on that track. However, as 1 is represented by a level of voltage and there is no break between successive bits, the receiver needs to know where one bit ends and the next starts. To get an idea of this, say “ah” three times without pausing or changing your voice. You could be saying three short “ahs” or one long “ah.” You didn’t know how long each “ah” should last. Components in a processor are set to follow a clock pulse that signals the cut off point between bits on a bus.
Although the coordinating mechanism is called a “clock” it is actually an electric current and current flows in cycles. So the speed of the CPU is set by the number of cycles of the clock signal per second. Cycles per second have a unit of measure call Hertz. So the speed of a CPU is measured in Hertz. As computers are so fast, their speed is noted in gigaHertz, which is a billion cycles per second.
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