Computer Organization and Architecture PDF

Computer Organization and Architecture Dr. Davies Rene Segera Department of Electrical and Information Engineering University of Nairobi Computer Organization and Architecture University of Nairobi Objective Objective To unders...

Computer Organization and Architecture Dr. Davies Rene Segera Department of Electrical and Information Engineering University of Nairobi Computer Organization and Architecture University of Nairobi Objective Objective To understand the difference between computer architecture and organization, and how these concepts affect the design and operation of computer systems. Learning Outcomes Identify and distinguish between computer architecture and computer organization. Explain the role of Instruction Set Architecture (ISA) in computer systems. Describe the importance of maintaining a distinction between architecture and orga- nization in computer design. Understand examples of architectural and organizational attributes. Discuss the impact of technological advances on computer architecture and organiza- tion. 1 Introduction In describing computers, we often differentiate between computer architecture and computer organization. Although these terms are used interchangeably sometimes, they refer to distinct concepts: 1.1 Computer Architecture Refers to the system’s features visible to the programmer, impacting how instructions are executed. An essential component of architecture is the Instruction Set Architecture (ISA), which defines: Instruction formats (layout of instructions) Opcodes (operation codes that specify the operation to perform) Registers (small storage locations within the CPU) Instruction and data memory (storage for program instructions and data) How instructions affect registers and memory. ISA directly affects how a program runs, making it crucial to the logical execution of programs. 1 Computer Organization and Architecture University of Nairobi 1.2 Computer Organization Refers to how the system’s hardware units work together to implement the architecture. This includes: Control signals (used for internal data handling within the computer) Interfaces with input/output devices The memory technology (e.g., DRAM or flash) used in the computer. Organization decisions impact performance, cost, and the physical structure of the computer but are often invisible to the programmer. 2 Examples of Architectural vs. Organizational De- cisions A decision about including a multiply instruction in a computer is architectural. Deciding how to implement that instruction, whether by using a special multiply unit or reusing the add unit, is an organizational decision. Architectural choices influence how a program is logically executed, while organiza- tional choices impact how fast and efficiently the hardware can execute the instructions. 3 Importance of Distinguishing Between Architec- ture and Organization Historically, the distinction allowed manufacturers to create different models within a single product line. For instance: Case Study: IBM System/370 Architecture IBM System/370 Architecture: First introduced in 1970, this architecture al- lowed various models with different organizational features but the same fundamen- tal design. This flexibility allowed customers to upgrade to faster or cheaper models without needing new software. In modern microcomputers (like personal computers), advances in technology of- ten influence both architecture and organization, making the relationship between them closer. The development of Reduced Instruction Set Computer (RISC) architec- tures is a good example. RISC computers simplify instructions for faster processing, blending architectural and organizational advancements. 2  Computer Organization and Architecture University of Nairobi 4 Key Takeaways Key Takeaways Computer architecture determines the logical execution of instructions and includes the ISA, registers, and instruction formats. Computer organization is the physical realization of the architecture and includes control signals, interfaces, and memory technology. Distinguishing between architecture and organization enables flexibility in model design, as seen in IBM’s System/370. Technological advancements affect both architecture and organization, particu- larly in microcomputers and RISC systems. 5 Exam-Based Questions Q1: Define computer architecture and computer organization and explain the dif- ference between them. Q2: What is Instruction Set Architecture (ISA), and why is it important in com- puter architecture? Q3: List and briefly describe three elements of the Instruction Set Architecture (ISA). Q4: Explain the role of registers in computer architecture. Q5: Why are control signals considered part of computer organization? Q6: How does the IBM System/370 architecture illustrate the distinction between architecture and organization? Q7: Describe an architectural decision and an organizational decision in the con- text of a computer’s design. Q8: How do input/output interfaces fit into computer organization? Q9: What impact does memory technology have on computer organization? Q10: Explain how advancements in technology can affect both computer architecture and organization, particularly in microcomputers. 3  Computer Organization and Architecture University of Nairobi Q11: Describe the concept of a Reduced Instruction Set Computer (RISC) and how it affects computer design. Q12: What are opcodes and how are they used in the Instruction Set Architecture? Q13: Why is it essential to maintain a distinction between architecture and organization in designing computer systems? Q14: How does memory addressing relate to computer architecture? Q15: Discuss the importance of maintaining compatibility in architectural design for computer families like the IBM System/370. 4