Computer Architecture Introduction

Computer Architecture - Introduction

• Architecture refers to attributes visible to the programmer, including the instruction set, data representation, I/O mechanisms, and addressing techniques.
• An example is whether a multiply instruction exists.
• Organization describes how features are implemented, encompassing control signals, interfaces, and memory technology.
• An example is whether a hardware multiply unit exists or if multiplication is achieved through repeated addition.

Structure and Function

• Structure describes how components relate to each other.
• Function details the operation of individual components within the structure.
• Computer functions include data processing, storage, movement, and control.

Operations

• Data movement: Data exchange between the computer and the outside world.
• Storage: Temporary storage of data currently being processed.
• Processing: Applying operations on data, potentially storing results back into memory.
• Processing from storage to I/O: Processing data stored in the computer to be output.

The Computer - Top Level Structure

• The computer consists of:
  • Input/output (I/O) units
  • Main memory
  • Central Processing Unit (CPU).
• The CPU has a control unit that handles data flow and an arithmetic logic unit (ALU) for calculations and logical operations.

The Processor

• CPU purpose: fetch and execute instructions.
• CPU components include:
  • Arithmetic Logic Unit (ALU): calculations and logical decisions.
  • Control Unit: controls data flow.
  • Cache: fast access to frequently used instructions and data.
  • Registers:
    • Program Counter (PC)
    • Memory Address Register (MAR)
    • Memory Data Register (MDR)
    • Accumulator (ACC)

Von Neumann Machines

• A computer architecture and organization model used by modern computers.
• Von Neumann machines use the stored-program concept, where data and programs are stored in the same memory.
• This enables the machines to modify their own programs or data.

Von Neumann Machines (Continued)

• The stored program concept entails main memory storing programs and data.
• An arithmetic logic unit (ALU) performs calculations on binary data.
• The control unit interprets and executes these instructions.
• Input/output (I/O) devices interact with the control unit.
• The IAS computer was a significant example, developed at the Princeton Institute for Advanced Studies between 1946 and 1952.

Computer Registers

• Registers are storage locations in the CPU.
• Memory Buffer Register (MBR): holds data to be written to/read from memory or I/O.
• Memory Address Register (MAR): specifies the memory location for data.
• Instruction Register (IR): holds the current instruction being executed.
• Instruction Buffer Register: temporarily holds the next instruction from memory.
• Program Counter (PC): holds the address of the next instruction.
• Accumulator (ACC): temporarily holds operands and results of ALU operations.

IBM Systems

• IBM has been a major producer of punched-card and stored-program computers, including models like the 701 (scientific) and 702 (business).
• They led to the 700/7000 series.

Transistors

• Transistors replaced vacuum tubes in computer components.
• They are smaller, cheaper, and generate less heat.
• Silicon-based solid-state devices invented at Bell Labs in 1947 marked the start of the second generation of computers.

Semiconductor Memory

• Semiconductor memory was first developed in 1970.
• It's faster and has a much greater capacity than core memory.
• Capacity roughly doubles yearly.

Evolution of Intel Microprocessors

• Intel's 4004 was a groundbreaking chip containing all CPU components on a single chip.
• It could handle addition and multiplication of 4-bit numbers.
• The 8008 was a follow-up 8-bit microprocessor, nearly twice as complex as the 4004 and designed for specific applications.
• Later processors like the 8086 and 80386 demonstrated increased capabilities (16-bit and 32-bit).

Speeding it Up

• Branch prediction: the processor anticipates which program branches will run next, speeding up execution.
• Data flow analysis: the processor determines which instructions depend on each other's results, creating a more optimized execution order.
• Speculative execution: processors compute instructions ahead of their execution order, handling results in temporary locations.

What is a Program?

• A program is a sequence of steps where each step involves an arithmetic/logical operation.
• Each operation requires unique control signals.

Function of Control Unit

• The control unit receives an operation code.
• It then issues the corresponding control signals.

Components

• The control unit and arithmetic logic unit (ALU) comprise the central processing unit (CPU).
• Input/output (I/O), memory, and storage are necessary for the system to function.

Instruction Cycle

• The instruction cycle includes the fetch and execute phases.
• Fetch retrieves the next instruction from memory.
• Execute interprets and implements the instruction.

Execute Cycle

• Processor-memory interaction, I/O operation, data processing, or control alteration (e.g., jump instructions).

Interrupts

• A mechanism through which other modules (e.g., I/O units) can interrupt the CPU's normal processing flow.
• Triggers for interrupts include program errors, timer events, I/O completion, or hardware failures.

Connecting

• All components must be interconnected.
• Different connection types are needed for the various parts (e.g., CPU, memory, I/O).

Memory Connection

• The memory transfers data, addresses, and control signals.

Input/Output Connection

• Data flows to and from peripherals in a similar way to memory.
• Peripheral devices get control signals from the computer system and send signals to the computer back.

CPU Connection

• The CPU reads instructions and data from memory.
• It writes data to memory after processing.
• It sends signals to other units, and responds to interrupts.

Buses

• Buses facilitate interconnections between different parts of the system.
• Common types include control, address, and data buses.

What is a Bus?

• A shared communication pathway.
• It usually broadcasts to all connected devices.
• Different channels can reside on a single bus.

Address Bus

• Distinguishes data sources and destinations.
• Bus width determines the maximum memory capacity.

Control Bus

• Transmission of control signals and timing information.
• Example signals include read/write, interrupt requests, and clock signals.

Memory Hierarchy

• Contains levels of memory arranged from fast to slow, and massive to small.
• This design prioritizes quicker access.
• The levels include registers, internal memory, cache, main memory, external memory (backing storage).

Memory Hierarchy - Diagram

• Illustrates the layered structure of memory (registers, cache, main memory, backing storage).

Performance

• Access time: time between presenting an address and getting valid data.
• Memory cycle time: accounts for time needed to recover for the next access, taking account of read and write operations.
• Transfer rate: speed of data movement.

Access Methods

• Sequential: Data access is ordered.
• Direct: Data access is based on a unique address and a search within a specific area.
• Random: Access time is independent of location or prior accesses (e.g., RAM).
• Associative: Data is found through comparison with stored data (e.g., cache).

Internal Memory

• RAM (Random Access Memory): Volatile memory capable of reading and writing.
• DRAM (Dynamic RAM): Simple chip structure but requires refreshing.
• SRAM (Static RAM): More complex structure, but faster and doesn't need refreshing.
• ROM (Read-Only Memory): Non-volatile, permanent storage for programs and data.

This quiz covers the fundamental concepts of computer architecture, outlining key distinctions between architecture and organization. It discusses the structure and function of components and their roles in data processing, storage, and movement. Test your understanding of these essential principles.