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HARDWARE - Coggle Diagram

- - - - Transmits the address between the processor and memory
      - Direction: Unidirectional: From the processor to memory and input-output devices
    - - Sends data between the processor, memory and input-output devices
      - Direction: Bi-directional
    - - Signals sent by processor to control the memory and peripheral devices
      - Direction: Unidirectional: From the processor to memory and input-output devices
  - - - The processor contains ALU (Arithmetic and Logic Unit) and Control Unit (CU).
    - - Control unit is responsible for controlling the memory, processor and input-output devices.
      - It contains the CIR (Current Instruction Register) and PC (Program Counter).
      - The CIR contains the current instruction carried out by the processor.
      - The PC contains the location of the instruction that is to be executed next.
      - The control unit reads the instructions from the memory, decodes it and sends control signals to the memory and input-output devices.
- - - - temperature
      - pressure
      - lights
      - motion
      - sound
- - - - A CPU consists of multiple processing units. Each processing unit is known as core.
      - A core consists of a processor (ALU and CU) and registers.
      - Computers may be dual (two), quad (four) or even more cores.
      - As the number of cores increases, the computer has more power to execute multiple programs at a particular instant of time.
      - When the number of cores is increased, the communication channels between the cores also use up some of the speed
      - Hence, increasing the number of cores four times will not increase the speed of computer of the computer four times.
      - cache size
        
        Cache is a small memory part located closer to CPU when compared to RAM.
        
        Cache temporarily holds the data and instruction that the CPU is likely to use more frequently.
        
        To reduce the access time, the control unit checks cache first before requesting any instruction from RAM or main memory.
        
        Accessing cache memory
        
        Due to the presence of cache, the speed of the CPU increases.
        
        As the cache is near to CPU, it is faster to use a cache when compared to RAM.
        
        It is important to note that cache occupies only a small physical space compared to RAM.
        
        Cache is also expensive when compared to RAM.
        
        If a computer has 8 CB of RAM, level 3 cache memory is only about 2-4 MB.
    - - THE TWO MAIN TYPES
        
        Complex Instruction Set Computing (CISC)
        
        Reduced Instruction Set Computing (RISC)
    - - Clock rate indicates the number of instructions processed by a CPU in a second.
      - It is measured in megahertz (MHz) or gigahertz (GHz).
      - A 4 GHz CPU processes about 4 billion instructions a second.
      - A faster CPU requires more power and thus, heat is generated. This heat is a form of power loss.
      - The speed of computer which is set by default can also be changed using BIOS.
      - Increasing the speed of the computer by increasing the CPU clock speed is called as over-clocking.
      - A CPU has circuitry limitations regarding the speed. If a computer is forced to work at a higher speed, more than its limit, the instructions might not get executed completely. This leads to data corruption and overheating.
- - - - PRIMARY MEMORY
        
        Primary memory is a type of memory that is accessed directly by the CPU. For example: RAM, ROM and cache.
        
        PRIMARY MEMORY IN CPU:
        
        registers
        
        cache
        
        Virtual memory
        
        RAM
        
        RAM is a temporary memory which stores data, files and parts of the operating system that is currently in use.
        
        When a program is loaded from the hard drive, all its contents such as its instructions and data are loaded to the RAM and the CPU accesses this information. It is also called the main memory.
        
        Used by the operating system, applications and any data that are currently used.
        
        The access time for a CPU to access any data from the RAM is less when compared to accessing data from a hard drive.
        
        The larger the size of RAM, the faster the computer operates
        
        Buffers also use RAM.
        
        When the power is lost, the contents of RAM are lost.
        
        The contents of RAM can be read from, written to and changed.
        
        Each memory location in RAM has a unique address.
        
        TYPES OF RAM:
        
        Dynamic RAM (DRAM)
        
        DRAM consists of transistors that act as switches and capacitors that hold binary data.
        
        DRAM has to be constantly refreshed (every 15 microseconds) to maintain the charge in the capacitor.
        
        DRAM is used for main RAM memory
        
        Static RAM (SRAM)
        
        SRAM uses ‘flip flops’ which hold each bit of memory.
        
        SRAM need not be refreshed constantly. SRAM is faster than DRAM.
        
        SRAM is used in cache memory.
        
        SRAM is more complex to build than DRAM and is therefore more expensive.
        
        Due to the complex design and more transistors and additional wiring required in SRAM, it offers smaller capacity compared to DRAM.
        
        But, the closer the memory type, the more expensive it is.
        The closer the memory type, the faster the access is
        
        fastest, smallest and most expensive memory to slowest, largest and least expensive: CPU registers, Cache, RAM Virtual memory(in Hard disk)
        
        LATENCY:
        
        time taken by components to respond to a request
      - SECONDARY MEMORY
        
        Secondary memory refers to the external storage devices such as hard drives, CD, flash drives, etc.