4.1 - Central Processing Unit (CPU) Architecture
Clock Cycle
Clock speeds are measured in terms of GHz; this is the vibrational frequency of the clock which sends out pulses along the control bus - a 3.5 GHZ clock cycle means 3.5 billion clock cycles a second
Interrupt
Signal sent from a device or software to a processor requesting its attention; the processor suspends all operations until the interrupt has ben serviced
Interrupt Service Routine (ISR) or Interrupt Handler
Software which handles interrupt requests (such as 'printer out of paper') and sends the request to the CPU for processing
Video Graphics Array (VGA)
Type of port connecting devices to a computer
Cache Memory
A high speed auxiliary memory which permits high speed data transfer and retrieval
Current Instruction Register
A register used to contain the instruction which is currently being executed or decoded
High-Definition Multimedia Interface (HDMI)
Type of port connecting devices to a computer
Special Purpose Registers in Processor Summary
1. Memory Address Register (MAR) - Holds the memory location of data that needs to be accessed 2. Memory Data Register (MDR) - Holds data that is being transferred to or from memory 3. Accumulator (AC) - Where intermediate arithmetic and logic results are stored 4. Program Counter (PC) - Contains the address of the next instruction to be executed 5. Current Instruction Register (CIR) - Contains the current instruction during processing
Quad Core
A CPU containing four cores
Dual Core
A CPU containing two cores
Fetch-Execute Cycle
A cycle in which instructions and data are fetched from memory and then decoded and finally executed
Program Counter (PC)
A register used in a computer to store the address of the instruction which is currently being executed
Universal Serial Bus (USB)
A type of port connecting devices to a computer
Core
A unit made up of ALU, control unit and registers which is part of a CPU. A CPU may contain a number of cores
Interrupt Priority
All interrupts are given a priority so that the processor knows which need to be serviced first and which interrupts are to be dealt with quickly
Data Bus
Allows data to be carried from processor to memory (and vice versa) or to and from input/output devices
BIOS
Basic input/output system
Control Bus
Carries signals from control unit to all other computer components
Address Bus
Carries the addresses throughout the computer system
Overclocking
Changing the clock speed of a system clock to a value higher than the factory/recommended setting
Arithmetic Logic Unit (ALU)
Component in the processor which carries out all arithmetic and logical operations
Control Unit
Ensures synchronisation of data flow and programs throughout the computer by sending out control signals along the control bus
Port
External connection to a computer which allows it to communicate with various peripheral devices. A number of different port technologies exist
Word
Group of bits used by a computer to represent a single unit
Immediate Access Store (IAS)
Holds all data and programs needed to be accessed by the control unit
Register Transfer Notation (RTN)
Short hand notation to show movement of data and instructions in a processor, can be used to represent the operation of the fetch-execute cycle
Flag
Indicates the status of a bit in the status register, for example, N = 1 indicates the result of an addition gives a negative value
High-Bandwidth Digital Copy Protection (HDCP)
Part of HDMI technology which reduces risk of piracy of software and multimedia
System Clock
Produces timing signals on the control bus to ensure synchronisation takes place
Asynchronous Serial Data Transmission
Serial refers to a single wire being used to transmit bits of data one after the other. Asynchronous refers to a sender using its own clock/timer device rather sharing the same clock/timer with the recipient device
Register
Temporary component in the processor which can be general or specific in its use that holds data or instructions as part of the fetch-execute cycle
Accumulator
Temporary general purpose register which stores numerical values at any part of a given operation
Von Neumann Architecture
The key elements of Von Neumann Architecture are: data and instructions are both stored in primary storage, instructions are fetched from memory one at a time and in order. Program and data are indistinguishable. It's architecture uses a single processor
Bidirectional
Used to describe a bus in which bits can travel in both directions
Unidirectional
Used to describe a bus in which bits can travel in one direction only
Status Register
Used when an instruction requires some form of arithmetic or logical processing