Section 5 Chapter 25 - Internal Computer Hardware Flashcards
Internal component
A component within the CPU
External component
A component outside the CPU
4 main internal components
- Processor
- Main memory
- Busses
- I/O Controllers
Components of the processor (3)
- Control Unit
- ALU
- Registers
Control unit
Coordinates and controls all the operations being carried out by the computer
How the control unit operates
Fetch-decode-execute cycle
Description of the fetch-execute-decode cycle
Fetch - causes the next instruction to be fetched from main memory
Decode - decodes the instruction
Execute - runs the instruction
ALU
Performs arithmetic/logic operations on data
Arithmetic operations
Addition, multiplication e.t.c
Logical operations
> , =,
Bitwise logical operations
AND, OR, NOT e.t.c.
Register
A memory cell that operates at very high speed
Bus
A set of parallel wires connecting two or more components of a computer
The three main busses
- Control
- Address
- Data
System bus
All the three main busses are system busses
What it means when it’s said that a bus is a shared transmission medium
Only one device can transmit at any one time
Which way can data flow on the busses
Control - 2 way
Address - 1 way (out of processor)
Data - 2 way
Purpose of the control bus
To transmit command, timing and status information between system components
Memory write (Control bus signal)
Data on the data bus is written to the address on the address bus
Memory read (Control bus signal)
Data from the addressed location is loaded onto the data bus
I/O Write (Control bus signal)
Data on the data bus is output to the addressed I/O port
I/O Read (Control bus signal)
Data from the addressed I/O port is placed on the data bus
Bus request (Control bus signal)
Indicates that a device is requesting to use the data bus
Bus grant (Control bus signal)
Indicates the CPU has given access to use the data bus
