Computer Architecture and Organisation - Introduction

Course Learning Outcomes (CLOs):
- Explain the structures and functions of primary computer components.
- Construct simple assembly language programs and programs for programmable peripheral interface devices.
- Formulate solutions for computer architecture and organization problems as a team.
Assessment Structure:
- Lab Reports: $25\%$ (Labs $4$ to $8$ ).
- Written Test: $25\%$
- Group Project: $50\%$ (Report and presentation, $4$ members per team).

ENIAC (Electronic Numerical Integrator And Computer):
- Developed by John Mauchly and John Eckert at the University of Pennsylvania ( $1943$ – $1946$ ).
- The world’s first general-purpose electronic digital computer.
- Characteristics: $30$ tons, $1500$ square feet, $18,000$ vacuum tubes, and $140\,kW$ power consumption.
- Capacity: $5000$ additions per second; decimal-based machine with manual programming via switches and cables.
IAS Computer (von Neumann Machine):
- Proposed the stored-program concept: instructions and data are stored in the same memory.
- Structure consists of the Central Processing Unit (CPU), Main Memory, and Input/Output (I/O) equipment.
- IAS Memory Formats: $4096$ storage locations (words) of $40\,bits$ each.
Key IAS Registers:
- MBR (Memory Buffer Register): Contains words to be stored in or received from memory/IO.
- MAR (Memory Address Register): Specifies the memory address for MBR operations.
- IR (Instruction Register): Holds the $8\,bit$ opcode being executed.
- IBR (Instruction Buffer Register): Holds the right-hand instruction from a memory word.
- PC (Program Counter): Contains the address of the next instruction pair.
- AC (Accumulator) and MQ (Multiplier Quotient): Temporarily hold operands and ALU results.
Commercial Computers:
- UNIVAC I: First successful commercial computer ( $1950$ ).
- IBM $701$ ( $1953$ ): Primary scientific focus; IBM $702$ ( $1955$ ): Business applications.

Second Generation: Transistors (1958–1964):
- Smaller, cheaper, and lower heat dissipation than vacuum tubes.
- Introduced high-level programming languages and system software.
- Digital Equipment Corporation (DEC) introduced the PDP-1 in $1957$ .
Third Generation: Integrated Circuits (1965–1971):
- Based on microelectronics: gates (data processing) and memory cells (data storage).
- Notable machines: IBM System/ $360$ and DEC PDP- $8$ .

Moore’s Law: Observed by Gordon Moore in $1965$ ; states the number of transistors on a single chip doubles approximately every $18$ months.
Consequences: Reduced costs, increased operating speeds due to shortened electrical paths, smaller physical sizes, and reduced power/cooling requirements.
Later Generations:
- LSI (Large Scale Integration).
- VLSI (Very Large Scale Integration).
- ULSI (Ultra Large Scale Integration).

Intel Milestones:
- $4004$ ( $1971$ ): First CPU on a single chip ( $4\,bit$ ).
- $8008$ ( $1972$ ): First $8\,bit$ microprocessor.
- $8080$ ( $1974$ ): First general-purpose microprocessor.
- $8086$ ( $1978$ ): First appearance of the x86 architecture ( $16\,bit$ ).
- $80386$ ( $1985$ ): First $32\,bit$ Intel machine; supported multitasking.
- Pentium Series: Introduced superscalar execution (parallel instructions) and multimedia enhancements (MMX).
- Core Series: Dual-core implementation ( $2006$ ) and transition to $64\,bit$ architectures.

Speed Techniques:
- Pipelining: Overlapping stages of instruction processing.
- Branch Prediction: Predicting which instruction groups are processed next.
- Data Flow Analysis: Optimizing schedules based on instruction dependencies.
- Speculative Execution: Executing instructions ahead of appearance using branch prediction.
Performance Balance: Adjusting architecture to mitigate component mismatches, such as widening DRAM paths, using multi-level cache hierarchies, and increasing bus bandwidth.
Current Obstacles: Power density/heat dissipation, RC delay (resistive-capacitive limits of thin wires), and the memory latency gap relative to processor speed.