Exploring IT: Theory Grade 11 - Hardware

CPU Design

• CPU Structure

  • Composed of two main sections:

    • Control Unit (CU)

    • Arithmetic Logic Unit (ALU)

  • Contains small storage locations called registers.

• CPU Connections

  • Connected to main memory via:

    • Address Bus: identifies memory addresses

    • Data Bus: transfers data

    • Control Bus: sends read/write control signals.

2.1 Control Unit (CU)

• Functionality:

  • Controls execution of instructions

  • Sends read/write signals to memory along with instruction/data addresses to fetch/store.

• Storage:

  • Fetched instructions/data are stored in CU registers or ALU registers.

2.1.2 Arithmetic Logic Unit (ALU)

• Purpose:

  • Performs calculations and logical comparisons.

  • Processed results are either stored back in memory or used immediately.

• Registers:

  • Current instruction is broken down and stored in registers.

  • Accumulator: stores the result of executions (data is loaded from and written back to RAM).

2.1.3 Registers

• Function:

  • Store current instructions and related data.

  • Built using Static RAM (SRAM): faster but more expensive, does not require refresh cycles.

• Bit Size:

  • Can be 32 bits or 64 bits.

  • 32-bit CPUs process 32-bit data in two stages; 64-bit CPUs can do it in one, improving performance.

• Performance Consideration:

  • 64-bit code increases memory consumption, could lead to more accesses to slower RAM.

2.1.4 Serial Processing

• Historical Context:

  • CPUs originally executed one instruction at a time sequentially.

  • Process broken into set instructions executed on a single core.

2.1.5 Parallel Processing

• Description:

  • Multiple instructions are executed simultaneously on different processors, improving speed.

• Can occur in two contexts:

  • Different parts of a problem executed in parallel

  • Different programs run on different processors concurrently.

2.1.5.1 Hyperthreading

• Developed by Intel:

  • Increases efficiency by allowing preloading of next instructions into a second set of registers.

  • Appears as if two instructions are executed simultaneously.

• Operating System Support:

  • Necessary for effective use; e.g. helps run different applications independently.

2.1.5.2 Multiprocessing

• Definition:

  • Uses multiple cores on a single CPU chip, allowing true simultaneous processing.

  • Requires support from the motherboard and operating system for efficiency.

2.1.6 Processor Cache

• Purpose:

  • Reduces idle time by storing frequently accessed data closer to the CPU.

• Cache Types:

  • Level 1 Cache (L1): Fastest, built-in CPU, small size.

  • Level 2 Cache (L2): Slightly slower, larger, might be located on-chip.

  • Level 3 Cache (L3): Largest, slowest, external to CPU but closest to it.

• Cache Hits and Misses:

  • Cache Hit: Data found in cache, faster access.

  • Cache Miss: Data not found in cache, longer access time required.

2.2 RAM (Random Access Memory)

• Description:

  • Main memory found on dedicated motherboard slots; stores currently used programs and data.

• Types of RAM:

  • Double Data Rate (DDR) SDRAM: Synchronous with CPU, allows faster data transfer.

  • Types include DDR, DDR2, DDR3, DDR4, with the latest iterations offering improved speed and efficiency.

2.2.1 Latency

• Definition:

  • Time taken for RAM to respond and process requests.

• L1 cache has less latency than L2, making it more efficient for quick access.

2.3 Motherboard

• Function:

  • Central printed circuit board connecting all components and devices, providing necessary bus connections.

2.3.1 System Clock

• Role:

  • Regulates the speed and timing of all computer operations via a crystal oscillator.

• Speed of the processor is measured in GHz.

2.3.1.1 Overclocking

• Definition:

  • Running computer components faster than their intended speed by adjusting clock settings, can lead to instability.

2.3.3 Internal Bus/Front Side Bus

• Internal Bus:

  • Connects CPU, RAM, and other components.

• Buses:

  • Data Bus: Transfers data.

  • Address Bus: Indicates memory addresses.

  • Control Bus: Carries instructions from CPU to other components.

2.4 Secondary Storage

• Description:

  • Includes hard drives and flash drives for data storage.

• Types:

  • HDDs: Can be mechanical or solid-state, varying in size, speed, and cost.

2.5 Other Types of Caching

• Disk Cache:

  • Improves read/write speeds of hard drives by storing frequently accessed data in faster memory.

• Browser Cache:

  • Stores copies of web pages for faster loading times.

• Web Cache:

  • Shared storing of previously accessed web content within a network to reduce loading times.