vonn neumann architecure Flashcards
What is stored program concept?
programs stored inside the computer that can be reprogrammed.
What does a processing unit contain?
- an arithmetic logic unit
- processor registers
What does a control unit contain?
- an instruction register
- a program counter
- memory that stores data + instructions
- external data storage
- input and output dates
fetch:
- CPU fetches data and instructions from the RAM and saves it in registers
- memory address of the next item that the CPU wants is put on the address bus.
- data from this memory address travels from RAM on the data bus.
decode:
the decode step involves the CPU and control unit working out what the instructions that it has just fetched actually mean.
execute:
- when the data processing happens
- instructions are carried out on the data. some instructions are carried out by the ALU (adding, shifting, AND, OR)
what is the clock
- determines the speed of the CPU. the chip uses a vibrating quartz crystal that maintains a constant rate of vibration.
- with every tick of the clock, the CPU fetches and executes one cycle.
- one cycle per second is known as 1 hertz.
- a CPU with a clock speed of 1 gigahertz can carry out one billion cycles per second.
- computer clocks have speeds of 3gz
the CPU (central processing unit)
hardware component responsible for all the processing that the computer carries out. its job is to process data.
the control unit
receives and sends signals to and from other components of the computer
responsible for handling hardware interrupts (eg. inputs from a mouse)
the ALU
performs actual operations on data.
this encompasses + / = *, booleans/logic gates (AND, OR).
registers:
extremely fast memory. located on the processor, and very very small.
bytes of data, aka immediate access storage.
it’s significantly faster than RAM as it doesn’t have to use buses.
cache:
high-speed memory used to store frequently accessed data or instructions.
closer to the CPU than main memory for faster access, improving system performance
stores frequently accessed data, e.g. game texture packs, fonts
instruction register
holds instructions executed by CPU
accumulator
holds ALU vales
program counter
holds the memory address of the next instruction to be fetched, like a person holding a flag
pipelining
a method of keeping all the components busy to improve overall CPU performance.
- an instruction completed every clock cycle, increases CPU throughout, optimising system performance
- a CPU is fully pipelined if a fetch can be carried out every clock cycle.
data bus
carries binary data from component to component. bidirectional
control bus:
carries signals that control the CPU components. bidirectional
address bus:
carries the address of a memory location. unidirectional
bus:
physical connection used to connect computer components to hardware and transfer data along them.
RAM
random access memory
read and write
stores instructions and data for the CPU to execute
if not enough, computer slowed down
volatile
1-256GB
ROM
read only memory
stores permanent instructions that start boot up
non volatile
6-8MB
solid state
no moving parts -> silent
lifespan 5y due to solid state degradation
stores data in electronic circuits
smaller than magnetic
larger but more expensive
fast read and write
non volatile
optical
distributes media and software
uses lasers to read and write data on reflective surface
small in capacity but cheap to make
