Systems Architechture, and Storage

The CPU
1. The CPU is like the 'brain' of the computer.
2. It stands for Central Processing Unit
3. It contains:
  1. Program Counter
    1. A special purpose register that holds the address of the next instruction to be executed
    2. The Program Counter points to the next instruction that needs to be executed It is located in the Control Unit The Program Counter is incremented after fetching an instruction This moves it on to point to the next instruction to be executed
  2. Control Unit
    1. The control unit coordinates all of the activities taking place within the CPU
  3. ALU
    1. The ALU or Arithmetic Logic Unit performs: Logical operations, shift operations and arithmetic operations
  4. General Purpose Registers
    1. Hold data, such as numbers during arithmetic calculations Some architectures have just a single register called the Accumulator
The Function and Characteristics of the CPU
1. The CPU functions by running a three-stage cycle: Fetch, Decode Execute. It's pretty self-explanitary.
2. The Arithmetic and Logic Unit (ALU) manages all operations to do with arithmetic and logic (surprise)
3. The Control Unit unit co-ordinates and controls all the operations carried out by the computer.
4. Processors
  1. One cycle per second = 1 Hertz (Hz) = 1 instruction carried out each second 1 Kilohertz (KHz) = 1000 cycles per second 1 Megahertz (MHz) = 1,000,000 cycles per second 1 Gigahertz (GHz) = 1,000,000,000 cycles per second (Approximately 1 billion!)
  2. A dual-core processor has two processors in the same integrated circuit, linked together A dual-core processor has twice the power but does not always perform twice as fast, because the software may not be able to take full advantage of both processors A quad-core processor has four linked processors
5. Cache Memory
  1. Cache is a small amount of very fast, expensive memory in the CPU It can be accessed faster than regular main memory (RAM)
  2. There are different ‘levels’ of cache: Level 1 cache is extremely fast but small (between 2-64KB), located very close to the processor Level 2 cache is fairly close to the processor, fairly fast and medium-sized (256KB-2MB) Some CPUs also have Level 3 cache, relatively large and close to RAM
6. Embedded Systems
  1. Examples of embedded systems would be like a satnav built into a car, a timer built into a microwave, or a heating system in a dishwasher
  2. An embedded computer is a single microprocessor that includes RAM, ROM and a CPU
  3. A single chip that contains all of the elements that are essential for any computer
Memory
1. RAM
  1. When an application or the operating system is run, it is copied from the hard disk into RAM
  3. Otherwise known as: Primary Memory, Main Memory, Core Memory and Central Memory
  4. The computer stores running programs and data in RAM when your computer is turned on
    1. When your computer is off, RAM is empty as it is volatile
    2. All your programs and data are safe on your hard disk
  5. Is the main memory that all your files etc. will get saved to . it can be read from and stuff is saved to it. It is very fastly accessible.
  6. When your memory is full, then files are saved to virtual memory. This is a section on the hardrive used as a sort of overspill; a reserve memory storage.
2. ROM
  1. Some data needs to be permanently held in memory, even when a computer has no power
  2. Essentially, the rom just holds the start-up codes.
  3. Stands for Read Only Memory
3. Flash Memory
  1. Flash memory is a type of non-volatile memory. this means that even when it is turned off/not in use, it still retains its data Furthermore, it is solid-state memory, so it is more robust and portable than a moving memory device, such as a hard disk driv
Storage

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