What is Computer Processor

Processors are now being built with even faster ratings. With all other parameters being equal (although they never are) a CPU operating at 500 MHz can process data five times as fast as one operating at 100 MHz

Types of Processors

CISC Processors

One of the earlier goals of CPU designers was to provide more and more instructions in the instruction set of a CPU, to ensure that the CPU directly supports more features, making it easier to translate high level language programs to machine language, and to ensure that the machine language programs run more effectively. Of course every additional instruction in the instruction set of a CPU requires the necessary hardware circuitry to handle that instruction, adding more complexity to the CPU’s hardware circuitry. Another goal of CPU designers was to optimize the usage of expensive memory. To achieve this, the designers tried to pack more instruction in memory, by introduction the concept of variable-length instructions such as half word, one and half word, etc.

For example and operand in an immediate instruction needs fewer bits, and can be designed as half word instruction. Additionally, CPU,s were designed to support a variety of addressing modes .CPUs with large instruction set, variable  length instructions and a variety of addressing modes are said to employ CISC(Complex instruction set computer) architectures, Since  CISC processors posses so many processing features, they make the job of machine language programmers easier. However they are complex and expensive to produce. Most personal computers of today use CISC processors.

RISC Processors

In early 1980;s Some CPU designers discovered that several of the instruction supported by a CISC-based CPU are rarely used. Hence they came out with an idea that the complexity of CPU design can be greatly reduced, by implementing only a bare minimum basic set of instructions, plus some of the more frequently used instructions in the hardware circuitry of the CPU. Other complex instructions need not to be supported in the instructions set of the CPU, because they can always be implemented in software, by using the basis set of instructions.

 While working on simpler CUP design. These designers also came up with the idea of making .All the instructions of uniform length, so that the decoding and execution of all instructions become simple fast. Furthermore, to speed up computation, and to reduce the complexity of handling a number of addressing modes, they decided to design all the instructions in such a way that they retrieve operands stored in registers in CPU, rather than from memory. These design ideas resulted in producing faster and less expensive processors. CPUs with a small instruction set, fixed-length instructions, and reduced reference to memory to retrieve operands, are said to employ RISC(Reduced Instruction Set Computers)architure, Since RISC processors have a small instruction set, they place extra demand on programmers, who must consider how to implement complex computations by combining simple instructions. However, due to simpler design, RISC processors are faster for most application, less complex and less expensive to produce than CISC processors.

EPIC Processors

The Explicitly Parallel Instruction Computing (EPIC) technology breaks through the sequential nature of conventional processor architectures, by allowing the software to communicate explicitly to the processor, when operations can be done in parallel. For this, it uses tighter coupling between the complier and the processor, and enables the compiler to extract maximum parallelism in the original code, and explicitly describe it to the processor. Processors based on EPIC architecture are simpler and more powerful than traditional CISC or RISC processors. These processors are mainly targeted to next-generation, 64-bit high-end server and workstation market (not for personal computer market).

What is instruction sets in computer architecture

Every CPU has built-in-ability to execute a set of machine instructions, called instructions set. Most CPUs have 200 or more instructions (such as add, substract, and compare) in instruction set. The machine language designed for a processor (CPU), is based on the list of instructions supported by the CPU in its instructions set. Since each processor (CPU).is based on the list instructions supported by the CPU in its instructions set, Since each processor has a unique instruction set, machine language programs written for one computer will generally not run on another computer, with a different CPU.

CPUs made by different manufacturers have different instructions sets. In fact, different CPU models of the same manufacturer also often have different instructions sets. However, manufacturers tend to group their CPUs into “families”, which have similar instructions sets. When a new CPU is developed, it it ensured that its instructions set includes all the instructions in the instruction set of its predecessor Crumples some new ones. This manufacturing strategy is known as upward compatibility, and the new CPU is said to be upward compatible with its predecessor. This feature allows software written for a computer with a particular CPU, to work on computers with newer processors of the same family. In turn, it allows the users of these computer systems to easily upgrade their system, without worrying about converting all their existing software.NSK2VZ4KNRW6

What is central processing unit (CPU) how it is work

The CPU is the brain of a computer system. All major calculations and comparisons performed by a computer are carried out inside its CPU.

 The CPU is also responsible for activating and controlling the operation of other units of the computer system. Hence, no other single component of a computer determines its overall performance ,as much as the CPU, In order to be able to quickly evaluate any computer capabilities it is important to know how CPU are internally structured how different CPUs differ from each other ,and how CPU speed is evaluated. These and other related concepts about CPU are described below.

The Control Unit.

We saw that the two basic components of a CPU are the control unit and the arithmetic logic unit. The control unit of the CPU selects and interprets program instructions, and then sees that they are executed. It has some special purpose registers (whose functions are described in a latter subsection), and a decoder to perform these activities. The special purpose registers, namely the Instructions register and the program control register, respectively hold the current instruction and the next instruction to be executed, and in this way help the control unit in instruction selection. On the other hand. The decoder has the necessary circuitry to decode and interpret the meaning of every instruction supported by the CPU. Each instruction is accompanied by microcode—very basic directions. Which tell the CPU how to execute the instruction?
Although, the control unit does not perform any actual processing of the data, it acts as a central nervous system for other components of the computer. It manages and coordinates the entire computer system, including the input and output units. It obtains instructions from the program stored in the main memory, interprets the instructions, and issues signal, which cause other units of the system to execute them.

The Arithmetic Logic Unit (ALU)

The ALU of the CPU is the place, where the actual execution of the instructions takes place, during the data procession operation. That is, when the control unit encounters an instruction, which involves an arithmetic operation (such as, add, subtract, multiply, divide), or a logic operation (such as less than, equal to, greater that), it passes control to the ALU. The ALU has some special purpose registers and the necessary circuitry, to carry out all the arithmetic and logic operations, which are included in the instructions supported by the CPU. For example, the arithmetic and logic operations, which are included in the instructions supported by the CPU.For example, the control unit might load two numbers into the registers in the ALU.Then, it might the ALU to add the two numbers (an arithmetic operations), or to check if the two numbers are equal (a logical operation).

In case of a microcomputer, the entire CPU (both the control unit and the ALU) is contained on a single tiny silicon chip, called a microprocessor.