2.3.1 Architecture Flashcards
Inputs
Keyboard
Mouse
Sensors
Computers take data
Process information (CPU)
Output information
Monitor or screen
CPU
Brain of the computer
- fetches instructions from RAM
- decodes instructions
- executes
- contains all other parts of hardware system - hard drives graphics sounds
What does the CPU contain
- control unit
- ALU
- registers
- CACHE memory
- modern computers have several CPUs
control Unit
- sends signals to control movement of data along busses
- controls how instructions are sequences in fetch execute cycle
- directs other parts of the system by sending control signals
ALU
Does the maths
Logical
Mathematical
Registers
- part of CPU
- immediate access store
- memory locations used to help control unit execute lines of code
- work at high speeds
- used in fetch execute cycle
Special purpose registers
- program counter- used to store address in memory RAM of next line of code to be executed
- MAR- location in memory of next line of code
- MDR- holds data held in the address from MAR that is waiting to be executed
- CIR- holds line of code processor currently executing
CACHE memory
- form of RAM that can be read/ written to at much higher speed
- located inside CPU
- stores instructions that CPU most frequently needs.
Program counter
Stores address in memory RAM of next line of code to be executed
MAR
Location in memory of next line of code
MDR
Holds data held in the address from MAR that is waiting to be executed
CIR
holds line of code processor currently executing.
Busses
Communication channels that allow data to flow between computer and components.
- channels that connect all the internal part of CPU together
- and CPU to other parts of the computer
- allow data to be sent and received as pulses of data
Address bus
- sends the address of the location in memory needed by the CPU
- data only flows in one direction
Carries the location in memory to be accessed for reading writing data
Data bus
Carries instructions or data between memory and CPU
Bidirectional flow
Control bus
Control signals can be sent back and fourth between processor and memory
Fetch execute cycle
Process used by a computer to retrieve a program instruction from memory, determine what instruction is expected to do and then carry out the actions associated with that instruction.
Process of fetch execute cycle
- load address into PC
- copy PC to MAR
- increment PC
- load data into MDR
- transfer data to CIR
- execute instruction in CIR
Input- output ports
Allow data to be transferred to or from peripheral devices to internal components of a computer.
Serial port
Parallel port
USB
Serial port
Bidirectional
- transmits one data bit at a time across a single wire.
Mainly for connections to mice and modems.
Parallel port
- sends all 8 bits at once over 8 wires in parallel
- connect old printers
USB
- sends data 1 bit at a time
- bidirectional
- provide high speeds
- connect most peripherals
Input/ output controllers
- connect busses to ports
- translates messages back and fourth between busses and peripheral
The clock
- small quartz crystal located in memory
- synchronises all computers instructions
- sends signal or pulse on a regular basis to all other computer components.
Factors influencing speed of processing
CLOCK SPEED- Increasing no. Of clock cycles per second means more instructions executed per second on motherboard.
- increasing clock speed not recommended as overheat internal component.
CACHE SIZE- instructions held in Cache are those CPUneeds most often.
- in cache- can be used at high speeds.
- more cache= instructions needed to operate faster can be accessed faster
PROCESSOR TYPE- processes with more cores will operate faster
- some offer 64 bit processing over 32 bit.
What is a port
A physical connection where peripherals can be connected to enable data transfer between devices and the processor.
Purpose of I/ O controllers in computer system
Busses control, send/ receive data
Component used to connect busses and ports (I/O)
The I/ O controller is between internal computer buses and port which communicates with external device.
Translates messages back and forth- between computer buses and the peripheral device.
Role of a processor during operation of a computer program
Consists of the CU series of registers and ALU
Fetched instructions from RAM
Decodes instructions
Controls hard drives, graphics, sound
Modern computers can have many CPU’s.
Act together to provide greater processing power.
How busses used in fetch execute cycle
Read signal sent via control bus to memory
Data transferred from memory to MDR via data bus.
First instruction address is loaded in to the program counter.
Contents are placed in MAR before the data can be accessed.
PC immediately updated to point to next location of instruction to be executed.
After being transferred by buses, instructions are copied in CIR where it is decided and executed by CPU.
How clock speed affects processing speed of computer.
If CPU requires specific number of clock cycles to execute instructions- increasing the clock rate can increase the number of instructions executed per second.
CPUs can be “over clocked”
Impact of different types of processor in speed of a computer system
RISC- smaller number of instructions at its disposal
During processing have to combine many simple instructions- an increased number of fetch execute cycles needed to carry out complex tasks- showing down speed of processing.
