Organization and Architecture of Computers

Source: freepik

In describing computers, a distinction is often made between computer architecture and computer organization. Although it is difficult to give an exact definition for these terms, there is consensus about the general areas covered by each.

Computer architecture refers to the attributes of a system that are seen by a programmer or, in other words, those attributes that have a direct impact on the logical execution of a program. A term that is often used interchangeably with computer architecture is instruction set architecture (ISA). ISA defines format instructions, instruction opcodes, registers, instructions and data memory; the effects of instructions executed on registers and memory; and an algorithm for controlling the execution of instructions.

Computer organizations refer to their operational and interconnection units which embody architectural specifications. Examples of architectural attributes include instruction sets, the number of bits used to represent various types of data (eg numbers, characters), I / O mechanisms, and techniques for handling memory. The organizational attributes include hardware details that are transparent to the programmer, such as control signals; interface between computer and peripherals; and memory technology used.

For example, it is a matter of architectural design whether computers will have it
multiplication instructions. It is an organizational problem whether the instruction will be implemented by a special multiplier unit or by a mechanism that makes repeated use of the unit added system. Organizational decisions can be based on the frequency of anticipating the use of multiplication instructions, the relative speed of the two approaches, and the cost and physical size of the specific doubling unit.

Historically, and still today, the difference between architecture and organization has become important. Many computer manufacturers offer a family of computer models, all with the same architecture but with differences in organization. As a result, different models within families have different price and performance characteristics. In addition, certain architectures can last for years and include a number of different computer models, the organization changing with technological change. A prominent example of these two phenomena is IBM System / 370 architecture. This architecture was first introduced in 1970 and 2007.

In a class of computers called microcomputers, the relationship between architecture and organization is very close. Changes in technology not only affect organizations but also result in the introduction of stronger and more complex building sciences. In general, there are very few requirements for generation-to-generation compatibility for these smaller machines. So, there is more interaction between the two organizational and architectural design decisions. An interesting example of this is computer instruction set reduced (RISC), which we study in the discussion of computer organization and computer architecture. The emphasis may be more on the organizational side. However, because computer organizations must be designed to implement certain architectures, specifications, thorough maintenance of the organization requires a detailed examination of the architecture as well.