4.7.1.1 Internal Hardware Components of a Computer

4.7.1.1 Internal Hardware Components of a Computer

1. Internal Components

   • The internal components of a computer system consist of the hardware required to store and process data, and communicate with external (peripheral) devices
   • Main Internal Components:
     • Procesor
     • Main Memory
     • Input / Output Controllers
   • Internal components are connected by the system bus

2. The Processor

   • Sometimes refered to as the CPU, the processor is the part of the computer that processes data by executing program instructions.
   • The processor's program instructions will be low-level instructions in the form of machine code that the processor has been designed to handle, based on a specific processor instruction set
   • For the processor to execute a program:
     • The program instructions need to be transferred from secondary storage into main memory
       • In main memory they can be decoded and executed
         • The data that is needed is also loaded into main memory from secondary storage or provided by the input / output devices

3. Main Memory

   • Memory that can be accessed directly by the processor
   • Each memory location where instructions or data are stored as binary sequences, has a physical address, which is a number used to locate that memory location and access its contents
   • There are two main types of main memory:
     • RAM
       • The 'working memory'
       • Used by the processor during the Fetch-Decode-Execute Cycle
     • ROM
       • Used in the boot process for the computer system

4. Input / Output Controllers

   • All external (peripheral) devices are connected to the processor through I/O Controllers.
     • E.g. Secondary Storage Devices
       • In contrast to main memory, Secondary Storage cannot be accessed directly by the processor
     • Can also be described as an interface between the core computer system and its peripherals

5. Buses

   • The components of a computer system are connected together using buses
     • Used to transfer data
   • System Bus
     • Address Bus
       • Used to specify the address of a memory location to either read (i.e. LOAD) data from or write (e.g. STORE) data to that memory location.
         • Uni-directional
         • Bigger Width = Increased maximum memory capacity
     • Data Bus
       • Used to transfer data and instructions
         • Bi-directional
         • Bigger Width = More data that can be fetched at one time
     • Control Bus
       • Used to send control signals that manage and orchestrate instructions/operations
         • Control Signals include:
           • Memory Read
           • Memory Write
           • Bus Request
           • Bus Grant
           • Bus Busy
           • Interrupt Request
           • Clock Signals
       • Bi-directional
   • One Way Conntections:
     • I/O Controller (Input) -> Data Bus
       • Data Bus -> I/O Controller (Output)
         • Processor -> Address Bus
           • Address Bus -> (ALL)
   • Two Way Conntections
     • Data Bus - I/O Controller (Sec. Storage)
       • Main Memory - Data Bus
   • Width
     • Refers to its number of parallel lines.
       • This determines the number of bits that can be transferred in one operation
         • e.g. If the width of the bus is 8 bits, then 2^8 bits can be transferred at one time

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