Processor

 The processor, also called the central processing unit (CPU), interprets and carries out the basic instructions that operate a computer. The processor significantly impacts overall computing power and manages most of a computer's operations. On larger computers, such as mainframes and supercomputers, the various functions performed by the processor extend over many separate chips and often multiple circuit boards. On a personal computer, all functions of the processor usually are a single chip. Some computer and chip manufacturers use the term microprocessor to refer to a personal computer processor chip.

 Most processor chip manufacturers now offer multi-core processors. A processor core, or simply core, contains the circuitry necessary to execute instructions. The operating system views each processor core as a separate processor. A multi-core processor is a single chip with two or more separate processor cores. Two common multi-core processor are dual-core and quad-core. A dual-core processor is a chip that contains two separate processor cores. Similarly, a quad-core processor is a chip with four separate processor cores.

 Each processor core on a multi-core processor generally runs at a slower clock speed than a single-core processor, but multi-core processors typically increase overall performance. For example, although a dual-core processor does not double the processing speed of a single-core processor, it can approach those speeds. The performance increase is especially noticeable when users are running multiple programs simultaneously such as antivirus software, spyware remover, e-mail program, instant messaging, media player, disc burning software, and photo editing software. Multi-core processors also are more energy efficient than separate multiple processor, requiring lower levels of power consumption and emitting less heat in the system unit.

 Processors contain a control unit and an arithmetic logic unit (ALU). These two components work together to perform processing operations.

The Control Unit

 The control unit is the component of the processor that directs and coordinates most of the operations in the computer. The control unit has a role much like a traffic cop: it interprets each instruction issued by a program and then initiates the appropriate action to carry out the instruction. Types of internal components that the control unit directs include the arihtmetic/logic unit, registers, and buses.

The Arithmetic Logic Unit

 The arithmetic logic unit (ALU), another component of the processor, performs arithmetic, comparison, and other operations.

 Arithmetic operations include basic calculations such as addition, subtraction, multiplication, and division. Comparison operations involve comparing one data item with another to determine wheter the first item is greater than, equal to, or less than the other item. Depending on the result of the comparison, different actions may occur. For example, to determine if an employee should receive overtime pay, software instructs the ALU to compare the number of hours an employee worked during the week with the regular time hours allowed (e.g., 40 hours). If the hours worked exceed 40, for example, software instructs the ALU to perform calculations that compute the overtime wage.

Machine Cycle

 For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle: (1) fetching, (2) decoding, (3) executing, and, if necessary (4) storing. Fetching is the process of obtaining a program instruction or data item from memory. The term decoding refers to the process of translating the instruction into signals the computer can execute. Executing is the process of carrying out the commands. Storing, in this context, mean writing the result to memory (not to a storage medium).

 In some computers, the processor fetches, decodes, executes, and stores only one instruction at a time. In these computers, the processor waits until an instruction completes all four stages of the machine cycle (fetch, decode, execute, and store) before beginning work on the next instruction.

 Most of today's personal computers support a concept called pipelining. With pipelining, the processor begins fetching a second instruction before it completes the machine cycle for the first instruction. Processors that use pipelining are faster because they do not have to wait for one instruction to complete the machine cycle before fetching the next. Think of a pipeline as an assembly line. By the time the first instruction is in the last stage of the machine cycle, three other instructions could have been fetched and started through the machine cycle.

Registers

 A processor contains small, high-speed storage locations, called registers, that temporarily hold data and instructions. Registers are part of the processor, not part of memory or a permanent storage device. Processors have many different types of registers, each with a specific storage function. Register functions include storing the location from where an instruction was fetched, storing an instruction while the control unit decodes it, storing data while the ALU computes it, and storing the results of a calculation.

The System Clock

 The processor relies on a small quartz crystal circuit called the system clock to control the timing of all computer operations. Just as your heart beats at a regular rate to keep your body functioning, the system clock generates regular electronic pulses, or ticks, that set the operating pace of components of the system unit.

 Each tick equates to a clock cycle. In the past, processor used one or more clock cycles to execute each instruction. Processors today often are superscalar, which means they can execute more then one instruction per clock cycle.

 The pace of the system clock, called the clock speed, is measured by the number of ticks per second. Current personal computer processors have clock speeds in the gigahertz range. Giga is a prefix that stands for billion, and a hertz ione cycle per second. Thus, one gigahertz (GHz) equals one billion ticks of the system clock per second. A computer that operates at 3 GHz has 3 billion (giga) clock cycles in oen second (hertz).

 The faster the clock speed, the more instruction the processor can execute per second. The speed of the system clock has no effect on devices such as a printer or disk drive. The speed of the system clock is just one factor that influences a computer's performance. Other factors, such as the type of processor chip, amount of cache, memory access time, bust width, and bus clock speed, are discussed later.

Comparison of Personal Computer Processor

 The leading manufacturers of personal computer chips are Intel and AMD. These manufacturers often identify their processor chips by a model name or model number. High-performance personal computers today may use a processor in the Intel Core family. Less expensive, basic personal computers may use a brand of Intel processor in the Pentium or Celeron family. The Xeon and Itanium families of processors are ideal for workstations and low-end servers.

 AMD is the leading manufacturer of Intel-compatible processors, which have an internal design similar to Intel processors, perform the same functions, and can be as powerful, but often are less expensive.

 In the past, chip manufacturers listed a processor's clock speed in marketing literature and advertisements. As previously mentioned, though, clock speed is only one factor that impacts processing speed in today's computers. To help consumers evaluate various processors, manufacturers such as Intel and AMD now use a numbering scheme that more accurately reflects the processing speed of their chips.

 Processor chips include technologies to improve processing performance, for example, to improve performance of multimedia and 3-D graphics. Most of Intel's processor chips also include vPro technology, which provides the capability to track computers hardware and software, diagnose and resolve computer problems, and secure computers form outside threats.

 As mentioned earlier, many personal computer processors are multi-core, with the processor cores working simultaneously on related instructions. These related instructions, called a thread, can be independent or part of a larger task. Software written to support multiple threads, called a multi-threaded program, run much faster than those in no threaded environments.

 Processors for traditional notebook computers and Tablet PCs also include technology to optimize and extend battery life, enhance security, and integrate wireless capabilities. For example, Intel's Centrino 2 mobile technology, which may have a Pro designator depending on its capabilities, integrates wireless functionality in notebook computers and Tablet PCs. Netbooks, smart phones, and other smaller mobile devices often use more compact processor that consume less power, yet offer high performance.

 Another type of processor, called system-on-a-chip, integrates the functions of a processor, memory, and a video card on a single chip. Lower-priced personal computers, Tablet PCs, networking devices, portable media players, and game consoles sometimes have a system-on-a-chip processor. The goal of system-on-a-chip manufacturers is to create processors that have faster clock speeds, consume less power, are small, and are cost effective.

Buying a Personal Computer

 If you are ready to buy a new computer, the processor you select should depend on how you plan to use the computer. To realize greater processing performance, you may want to choose a multi-core processor.

 Instead of buying an entirely a new computer, you might be able to upgrade your processor to increase the computer's performance. Be certain the processor you by is compatible with your computer's motherboard; otherwise, you will have to replace the motherboard, too. Replacing a processor is a fairly simple process, whereas replacing a motherboard is much more complicated.

Processor Cooling

 Processor chips generate quite a bit of heat, which could cause the chip to burn up.although the computer's main fan generates airflow, many of today's personal computer processors require additional cooling. Heat sinks/pipes and liquid cooling technologies often are used to help dissipate processor heat.

 A heat sink is a small ceramic or metal component with fins on its surface that absorbs and disperses heat produced by electrical components such as a processor. Some heat sinks are packaged as part of a processor chip. Others are installed on the top or the side of the chip. Because a heat sink consumes extra space, a smaller device called a heat pipe cools processors in notebooks and Tablet PCs.

 Some computers use liquid cooling technology to reduce the temperature of a processor. Liquid cooling technology uses a continuous flow of fluid(s), such as water and glycol, in a process that transfers the heated fluid away from the processor to a radiator-type grill, which cools the liquid, and then returns the cooled fluid to the processor.

 Some mobile computers and devices often have Low Voltage or Ultra Low Voltage (ULV) processors, which have such low power demands that they do not require additional cooling.

Parallel Processing

 Parallel processing is a method that uses multiple processors simultaneously to execute a single program or task. Parallel processing divides a single problem into portions so that multiple processors work on their assigned portion of the problem at the same time. Parallel processing requires special software that recognizes how to divide the problem and then bring the results back together again.

 Some personal computers implement parallel processing with dual-core processors or multi-core processors. Others have two or more separate processor chips, respectively called dual processor or multiprocessor computers.

 Massively parallel processing is large scale parallel processing that involves hundreds or thousands of processors. Supercomputers use massively parallel processing for applications such as artificial intelligence and weather forecasting.