THE CONCEPT OF COMPUTER ARCHITECTURE

1. THE CONCEPT OF COMPUTER ARCHITECTURE Chapter No. 2

2. Evolution of the Concept of Computer Architecture • The term computer architecture evolved in1964 by the chief architects of IBM System/360. • They interpreted computer architecture as the structure of machine that the assembly language programmer must understand to write a correct program for a machine. • Bell and Newell in 1970 gave the concept of computer architecture by introducing a hierarchical , multilevel description. They identified four levels as the electronic circuit level, the logic design level, the programming level, and the processor-memory-switch (PMS) level.

3. Evolution of the Concept of Computer Architecture • Sima in 1977 and Dasgupta in 1981 extend the concept by introducing the two dimensional concept of computer architecture which is equally distributed to functional specification and and the hardware implementation.

4. Recent Interpretation of the Concept of Computer Architecture • Now the interpretation of computer architecture covers the three aspects: • underlying computational model • Von Neumann, dataflow, … • Level of consideration • micromachine, processor, computer system • Scope of interest • functional specification, implementation

5. Underlying computational model Level of consideration Scope of interest Recent Interpretation of the Concept of Computer Architecture

6. Underlying Computational Model

7. Level of Abstraction

8. Scope of interest Functional specification Implementation Computer Computer Black box view Internal structure and operation Abstract architecture(logical architecture, external architecture, exo architecture, behavioral description, programming model) Concrete architecture (physical architecture, internal architecture, endo-architecture, structural architecture) Scope of Interest

9. Interpretation of the Concept of Computer Architecture at Different Levels of Abstraction • The term computer architecture can be used at any level depending upon the scope interest. • If scope of interest is functional then architecture is termed as abstract. • If scope of interest is implementation then architecture is termed as concrete.

10. Abstract Architecture • Also known as exo-architecture,external or logical architecture, a black box description, or in certain context as a programming model or a behavioral description. • The abstract architecture is the black box specification and considers two different point of views: • programmers point of view • dealing with the programming model • hardware designer’s point of view • dealing with the hardware model. It also incorporates additional specifications like interface protocols

11. Concrete Architecture • Also known as endo-architecture, internal or physical architecture or structural description. • How a computer is implemented at a particular level of abstraction. • E.g. at the system level the description of the concrete architecture is based on processor level building blocks, such as processors, memories,buses and so on. • The concrete architecture also considers two different point of views: • logic design • physical design

12. Concrete Architecture • Physical design • based on concrete circuit elements used, the specifications of signals, the interconnection of circuit elements, the declaration of initiated signal sequences. • Logic design • logic design is an abstraction of physical design. • The declaration of logical components used such as registers, execution units etc, their interconnections and the specification of the sequence of information transfers, which are initiated by each declared function.

13. Concrete Architecture of Computer System

14. Abstract Architecture of Processors (Architecture) • The abstract architecture of a processor is often referred to as simply the architecture of the processor

15. I/O interface Abstract Architecture of Processors (Architecture) • The hardware model of the processor is a description from the hardware designer’s point of view. Here, the processor is considered as a building block of a computer system. This can be specified by three interfaces: the programming interface, the interrupt interface and the I/O interface

16. Concrete Architectures of Processors (Micro Architecture) • The concrete architecture of a processor is often referred to as the microarchitecture.

17. Abstract Architecture of an Operating System • The abstract architecture of an operating system means the functional specifications.

18. Application programs Application program interface I/O controller Operating system Logical I/O interface User interface Data carrier interface Data Carrier Abstract Architecture of an Operating System

19. Concrete Architecture of an Operating System • In order to interpret the concrete architecture of an operating system, its building blocks, their interconnections and its operation have to be specified. • In this case, the building blocks are the main components of the operating system, such as memory management, processor management, I/O management, and so on.

20. Description of architectures Informal description Formal description Description Of Computer Architectures