What is the purpose of a CPU ?
To process all data and instructions
What is the function of the program counter (PC) ?
Hold the memory address of the next instruction
What is the function of the MAR ?
Holds the memory address about to be used by the CPU
What is the function of the MDR ?
Holds the actual data / instructions that has been fetched from main memory
What is the function of the accumulator ?
Stores all intermediate results of calculations
What is the function of the ALU ?
Does arithmetic calculations
What is the function of the control unit ?
Controls the flow of data in and out of CPU / manages FDE cycle
What is the function of cache ?
Stores regularly used data for quick access. Low capacity / expensive
What happens at the fetch stage FDE cycle ?
Memory address copied from PC to MAR
Using address in MAR, instruction is fetched from main memory and stored in MDR
PC is incremented to next instruction
What happens at the decode stage of the FDE cycle ?
Instruction in MDR is decoded by control unit
What happens at execute stage of FDE cycle ?
Decoded instruction carried out
E.g. Do a calculation
What are the 3 factors that affect CPU performance ?
Number of cores
Clock speed
Cache size
How does number of cores affect CPU performance ?
Each core process data therefore more cores = more instructions carried out per second
How does clock speed affect CPU performance ?
Higher clock speed mean higher number of instructions a single core can carry out per second
How does cache size affect CPU performance ?
Large cache = CPU has faster access to more storage
What is an embedded system ?
Small computers built into other devices
What are 3 advantages of embedded systems ?
Easy to design
Cheap to produce
Efficient at their task
What are 3 examples of embedded systems ?
Dishwasher
Microwaves
Sat nav
