Basic Computer Components & CPU Architecture

Basic Computer Components

• A computer system comprises several interconnected components working together.
• Central Processing Unit (CPU): The "brain" of the computer, performing calculations and controlling other components.
• Memory: Stores data and instructions for the CPU. RAM (Random Access Memory) is volatile, losing data when power is off. ROM (Read-Only Memory) is non-volatile, holding permanent instructions.
• Input/Output (I/O) devices: Allow interaction with the outside world, like keyboards, mice, screens, printers.
• Buses: Electrical pathways that facilitate communication between components. They can be address, data, or control buses.
• Arithmetic Logic Unit (ALU): A component of the CPU that performs arithmetic and logical operations.

CPU Architecture

• CPU design varies among different processors.
• Fetch-Decode-Execute Cycle: A fundamental cycle of operations the CPU performs. Fetching an instruction, decoding it, and executing the instruction.
• Registers: Small, fast storage locations within the CPU used for temporary data storage during calculations.
• Control Unit (CU): Part of the CPU that coordinates and manages the entire fetch-decode-execute cycle.

Memory Organization

• Memory is organized in a hierarchy, from fast, expensive cache memory to slower, larger main memory (RAM).
• Cache memory: Holds frequently accessed data and instructions from main memory to speed up processing.
• Main Memory: Stores data and instructions currently being used by the CPU.
• Secondary Storage: Permanent storage (e.g., hard drives, SSDs) that holds data even when the power is off.

Instruction Set Architecture (ISA)

• Defines how the CPU interacts with other components. Different ISAs lead to compatible, but not interchangeable, computer systems.
• Instructions are represented by binary codes. The instruction set varies among different CPUs.
• Assembly language: A low-level programming language that uses mnemonics to represent instructions.
• Machine language: The actual binary code representation that the CPU executes directly.

Instruction Formats

• Instructions are encoded in specific formats. Instruction format varies by operation and data type.
• Addressing Modes: Different methods to specify data locations, including register addressing, memory addressing, immediate addressing, etc.

Data Representation

• Data is stored in binary format. This includes numerical (integers, floating-point numbers) and non-numerical (character and special symbols) data.
• Different representations exist for varying data types, such as signed and unsigned integers. These dictate the range representable in binary.
• Data size is crucial for both memory usage and the CPU's arithmetic performance.

Input/Output (I/O) Systems

• I/O devices are crucial for interacting with the external world.
• Different mechanisms handle I/O, including programmed I/O, interrupt-driven I/O, Direct Memory Access (DMA).
• DMA allows devices to access main memory directly, bypassing the CPU for high-speed data transfer.

Instruction Pipelining

• Pipelining is a technique to improve CPU performance by overlapping the execution of multiple instructions.
• Stages in the pipeline include instruction fetching, decoding, execution, memory access, and write-back.
• Pipelining increases throughput, but stalls and hazards can occur.

Memory Hierarchy

• The memory hierarchy considers trade-offs between speed, cost, and capacity.
• Registers have the fastest access time, cache memory is very fast, main memory is reasonably fast, and secondary storage is the slowest.
• Level 1 (L1) cache, Level 2 (L2) cache, Level 3 (L3) cache, and main memory are all different stages in the memory hierarchy. The memory hierarchy's structure enables the highest and lowest levels to be accessed by programs or applications.

Parallel Processing

• Parallel processing involves using multiple processors to perform computations simultaneously.
• Multi-core processors: One chip with multiple CPUs within it to improve overall performance.
• Multiprocessing: Multiple separate computers working together on a shared task.

System Buses

• System buses connect various components within a computer system.
• Data bus: Carries data between components.
• Address bus: Specifies the location of data in memory.
• Control bus: Manages signals for the components.

Impacting Factors on Computer Performance

• Clock speed: Higher clock speed theoretically leads to faster processing.
• Instruction set architecture complexity: Complex ISAs might require more time for decoding.
• Memory access speed: Slow memory access can bottleneck performance.
• Cache memory capacity: Larger caches mean faster access to frequently used data.
• Number of cores/processors: Parallel processing utilizing multiple CPUs or multiple cores in a single CPU.