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2.2.1 Architecture (Internal Components (Processor- Main part of the…
2.2.1 Architecture
Internal Components
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Control Unit- The control unit is a digital circuit that: - Co-ordinates the movement of data
The CU gets each instruction in sequence.
Arithmetic Logic Unit (ALU) - This forms part of the processor.
It carries out mathematical, boolean and logical operations.
Logical operations allow you to make use of logical IF statements.
The Clock - timing signals are provided by an internal clock.
Clock speed is usually expressed in megahertz (MHz) or Gigahertz (GHz)
Memory
Main Memory (Random Access Memory (RAM)- Stores a portion of the operating system, application software currently running and other data items the processing unit needs when carrying out operations. Main memory is volatile (data will be lost).
RAM (Random Access Memory) - Volatile memory, when a computer is switched off the contents are lost.
- Used for holding programs and data the user is working with.
- RAM can be written to and form.
ROM (Read Only Memory) - Non- volatile (permanent) memory.
- ROM can be read from but NOT written to.
- The main use of ROM is to store the 'boot up' or BIOS (Basic Input/output System)
Cache- Part of the main store between the central processor and the rest of the main store. It is extremely fast to access, so sections of a program and its associated data are copied there to take advantage of its short fetch execute cycle. The use of cache greatly reduces processing time.
Why is Cache memory useful? - Helps solve the time delay between RAM and processor
- Data instructions which are used regularly are copied into the cache
- When the CPU needs this data the it can be retrieve it much quicker from the cache than it could from RAM
Types of Computer Ports
Serial Ports- A serial port transmits one data bit at a time across a single wire, used mainly for connections to mice and modems. Used for long distance but can be expensive.
Parallel Port- A parallel port transmits multiple bits of data over multiple wires at one time and can be used to connect some printers too. Used over short distances and is fast.
USB (Universal Serial Bus) - ports provide a high speed serial connection to most types of USB peripheral devices. Short- distance digital data communications. Can also supply electric power across the cable to devices that need it.
Multi-Tasking
Is the method of organising computer use that allows several different tasks or applications to be available at the same time. Modern Operating Systems allow users to have several tasks apparently running at the same time, with the user switching freely between applications or tasks.
Buses
A bus is basically a set of physical connections in the form of a set of physical cables or printed circuits used to connect various hardware components used in the execution of a set of instructions.
Address Bus: Will be used to identify a physical location in memory to be accessed. The location may be accessed to read data from or write data to memory. If an item of data is to be stored in memory the location to be used as a repository for the data item will be identified using the address bus.
Data Bus: Allows for the transfer of data between one component of a processor or computer system and another. If an item of data is to be stored in memory, the data item will travel to the memory location via the data bus.
Control Bus: Carries commands from the CPU to other devices in relation to the instructions being executed at a particular time. If an item of data is to be stored in memory the control bus will carry the write command to the memory location.