Unit 2 Computer Systems Flashcards
What is Von Neumann Architecture made up of
It has a CPU with a single control unit, It has ALU with processor registers
What does the Von Neumann Model do
It fetches instructions from memory, decodes and executes them. This is not a very efficient model but it is simple
What is the 3 step cycle used by the CPU to process data
Fetch - Decode - Execute cycle
What is Fetch in the Fetch - Decode - Execute cycle
Instructions are loaded into RAM before the processor starts running the program
What is Decode in the Fetch - Decode - Execute cycle
The binary representation of an instruction needs to be decoded before it can be run. This is the process the Control Unit uses to work out what the other components need to do.
Each processor will have slightly different encodings for instructions
What is Execute in the Fetch - Decode - Execute cycle
Once the instruction is understood, the instruction will be executed. The Control Unit tells the other components what they need to do in order for the instruction to work
How does the CPU use Fetch
Control Unit sends the fetch instruction
ALU adds one to program counter
Buses carry the instruction to memory and carry the data back
MAR holds the address to fetch the instructions from
MDR receives instruction fetched from RAM
CIR gets a copy of the instruction
Program counter goes up by one
How does the CPU use Decode
Control Unit decodes the instruction
Buses carry the instruction to the Control Unit
CIR provides the instruction to the Control Unit
How does the CPU use Execute
Control Unit tells other components what they need to do
ALU performs calculations
Busses carry and data required or received from the instruction
Accumulator holds any data that is produced
