1. Computer Architecture 2 nd year (computer and Information Sc.) haboulenien@hotmail.com

2. Grading Assessment Grade  Final Exam 50  Mid-Term Exam 25  Class Work 10  Other Activities and/or exams 15

3. Contents  Computer Function and Interconnection  Instruction Sets Characteristics and Functions Addressing modes  Cache and internal Memory  CPU and Control unit operation  Input/Output  Multiprocessor and alternative architectures  Performance enhancement

4. References Computer Organization and Architecture, 8 th Ed., (or Later) W. Stallings Computer Organization and Design 4 th Ed., (or Later) D. Pattarson and J. Hennessy

5. WHY STUDY COMPUTER ARCHITECTURE?  The IEEE/ACM Computer Curricula lists computer architecture as one of the core subjects that should be in the curriculum of all students in computer science and computer engineering. The report says the following: “The computer lies at the heart of computing. Without it most of the computing disciplines today would be a branch of theoretical mathematics. To be a professional in any field of computing today,

6. one should not regard the computer as just a black box that executes programs by magic. All students of computing should acquire some understanding and appreciation of a computer system’s functional components, their characteristics, their performance, and their interactions. There are practical implications as well. Students need to understand computer architecture in order to structure a program so that it runs more efficiently on a real machine. In selecting a system to use, they should be able to understand the tradeoff among various components, such as CPU clock speed vs. memory size.”

7. Computer Architecture (definition)  Computer architecture describes the main attributes of a system visible to a programmer, that have direct impact on logical execution of a program. Examples of architectural attributes include instruction set, the number of bits used to represent various data types ( e.g., numbers, characters), I/O mechanisms, and techniques for addressing memory.

8. Architecture & Organization 1  it is an architectural design issue whether a computer will have a multiply instruction.  It is an organizational issue whether that instruction will be implemented by a special multiply unit or by a repeated use of the add unit of the system.

9. Architecture & Organization 2  All Intel x86 family share the same basic architecture  The IBM System/370 family share the same basic architecture This gives code compatibility (at least backwards)  Organization differs between different versions (different price and performance characteristics)

10. Structure & Function  A computer is a complex system. How can one clearly describe it? The key is to recognize the hierarchical nature of most complex systems, including the computer. A hierarchical system is a set of interrelated subsystems, each of the latter, in turn, hierarchical in structure  Structure is the way in which components relate to each other  Function is the operation of individual components as part of the structure

11. A functional view of the computer

12. Function  Computer functions are: Data processing Data storage Data movement Control

13. Structure - Top Level Computer Main Memory Input / Output System Interconnection Peripherals Communication lines Central Processing Unit Computer

14. Function  (CPU or processor): Controls the operation of the computer and performs its data processing functions  Main memory: Stores data  I/O: Moves data between the computer and its external environment  System interconnection (system bus): provides mechanism for communication among CPU, main memory, and I/O

15. Structure - The CPU Computer Arithmetic and Login Unit Control Unit Internal CPU Interconnection Registers CPU I/O Memory System Bus CPU

16. Function  Control unit: Controls the operation of the CPU and hence the computer.  ALU: Performs the computer’s data processing functions.  Registers: Provides storage internal to the CPU.  CPU interconnection: provides mechanism for communication among the control unit, ALU, and registers

17. Structure - The Control Unit CPU Control Memory Control Unit Registers and Decoders Sequencing Logic Control Unit ALU Registers Internal Bus Control Unit

18. von Neumann architecture  Data and instructions are stored in a single read–write memory.  The contents of this memory are addressable by location, without regard to the type of data contained there.  Execution occurs in a sequential fashion (unless explicitly modified) from one instruction to the next.

19. What is a program?  A sequence of steps  For each step, an arithmetic or logical operation is done  For each operation (e.g. ADD, MOVE) a unique code is provided  For each operation, a different set of control signals is needed  A hardware segment accepts the code and issues the control signals

20. Program Concept

21. Components  The Control Unit and the Arithmetic and Logic Unit constitute the Central Processing Unit  Data and instructions need to get into the system and results out Input/output  Temporary storage of code and results is needed (stored-program concept) Main memory

22. Software and hardware: Hierarchical view

23. Below your program

24. Computer Components: Top Level View

25. Registers 1  Memory buffer register (MBR): Contains the data to be written into memory or receives the data read from memory  Memory address register (MAR): Specifies the address in memory for the next read or write  Similarly, an I/O address register (I/OAR) and an I/O buffer register (I/OBR) are used between I/O module and the CPU

26. Registers 2  Instruction register (IR): Contains the instruction being executed  Program counter (PC): Contains the address of the next instruction to be fetched from memory

27. CPU Operation  The processor executes the program by reading (fetching) it from memory, instruction by instruction, and executing each instruction.  These steps are known as: the instruction cycle 1.Read (fetch) the next instruction from memory 2. Execute the instruction

28. Instruction Cycle Fetch Execute

29. Fetch Cycle  Program Counter (PC) holds address of next instruction to fetch  Processor fetches instruction from memory location pointed to by PC  Increment PC (Unless told otherwise)  Instruction loaded into Instruction Register (IR)

30. Execute Cycle 1 Processor interprets instruction and performs required actions. In general these action falls into:  Processor - memory data transfer between CPU and main memory  Processor - I/O Data transfer between CPU and I/O module

31. Execute Cycle 2  Data processing Some arithmetic or logical operation on data  Control Alteration of sequence of operations e.g. jump (branch)

32. Example of Program Execution 1

33. Example of Program Execution 2

34. RQ: 1.2, 1.3, 1.4, 1.5, 3.1 P:3.1, 3.2, 3.3, 3.4

35. Chapter 1 Chapter 3 up to page 72