Overview
This lecture introduces computer hardware concepts focused on the CPU, key internal components, and the basics of computer memory and bus systems, as part one of computer architecture.
Hardware Basics
- Hardware refers to all tangible, physical computer components, including input/output devices, storage, and internal parts.
- Examples: keyboard, mouse, monitor, sensors, printers, internal memory, storage drives, and external storage devices.
Central Processing Unit (CPU)
- The CPU (or microprocessor/processor) is the "brain" of the computer, controlling all operations and device communications.
- CPUs are often integrated circuits on a single microchip in all modern devices.
Von Neumann Architecture
- Developed in the 1940s, von Neumann architecture introduced the stored program concept, allowing programs and data to be stored in memory.
- Features include a CPU that accesses memory directly, sequential instruction execution, and memory storing both data and programs.
Components Inside the CPU
- The CPU contains three main parts: the Control Unit (CU), Arithmetic Logic Unit (ALU), and registers.
- The system clock synchronizes all CPU operations, with clock speed measured in hertz (Hz); higher speeds mean more instructions per second.
Memory and Storage
- The CPU loads programs from the hard disk into RAM for faster access and processing.
- RAM is used for temporary storage of data and instructions due to its speed advantage over hard disks.
Control Unit, ALU, and Registers
- The Control Unit fetches, decodes, and manages instructions, maintaining synchronization in the system.
- The ALU performs arithmetic (add, subtract, shift) and logic (and, or) operations; multiple ALUs may exist for efficiency.
- Registers are small, fast memory locations inside the CPU, holding data, instructions, and addresses during processing.
Key Registers
- Common registers: Program Counter (PC), Current Instruction Register (CIR), Accumulator (ACC), Memory Address Register (MAR), Memory Data Register (MDR).
- Registers store current instructions, next addresses, results, and data for quick access.
Bus Systems
- Three main buses connect CPU, memory, and I/O devices:
- Address Bus: carries memory addresses from CPU to components.
- Control Bus: sends control signals and clock pulses from CPU.
- Data Bus: transfers actual data between CPU and other parts.
Memory Structure and Data Transfer
- Memory is organized in partitions consisting of an address (location) and content (data).
- The MAR holds memory addresses; the MDR (or buffer) holds data to be read or written.
- Reading from memory: address placed in MAR, read signal sent, data placed in MDR.
- Writing to memory: data placed in MDR, address in MAR, write signal sent to store data.
Key Terms & Definitions
- CPU (Central Processing Unit) — Main processor controlling computer operations.
- Von Neumann Architecture — Computer design model storing data and instructions in memory.
- Control Unit (CU) — Directs processing operations and synchronizes data flow.
- Arithmetic Logic Unit (ALU) — Performs mathematical and logical tasks.
- Register — Small, fast memory inside the CPU for temporary data storage.
- System Clock — Synchronizes CPU operations, measured in hertz (Hz).
- Bus — Pathways for data, addresses, and control signals (address, control, data bus).
- RAM (Random Access Memory) — Fast, temporary memory for active processes.
Action Items / Next Steps
- Review chapter one for more detail on shifting and ALU functions.
- Prepare for next lesson on the Fetch-Decode-Execute cycle.