What is a CPU?
Central Processing Unit made of silicon and has billion of switches inside.
Carries out all the commands and processes information.
What is clock speed?
Measured in Hz and corresponds with how many FDE cycles the CPU can do in a second:
4GHz= 4 billion FDE cycles per second.
What is cache?
Storage location faster than RAM.
Stores commonly used instructions (don’t have to go to CPU to FDE).
Volatile and small.
How does the number of cores affect CPU speed?
Cores act as another CPU:
More cores = more instructions carried out.
Only useful when the applications are programmed to handle it.
What does the PC do?
Stores the address of the next instruction to be run
Increments by 1 each time
What does the ACC do?
Holds the data (number) that you are currently working on / result from ALU.
What does the MAR do?
Contents of the PC are copied here.
Stores the address where the next data will be fetched from
What does the MDR do?
Stores data / instructions being brought back from the RAM.
What does the CIR do?
The instructions / data in the MDR are copied here.
What does the data bus do?
Carries data around (can go both ways).
What does the address bus do?
Carries around addresses (can only go one way).
What does the control bus do?
Sends signals to the RAM to either re-write or bring the data back.
What does the Arithmetic Logic Unit (ALU) do?
Does the arithmetic (mathematical) and logic calculations within the computer.
What does the Control Unit (CU) do?
Manages the data:
Controls where data goes and monitors the flow of data.
Sends control signals between the different internal components.
What is Von Neumann architecture?
Data + instructions are stored in the same RAM location.
FDE cycle is then used to FDE the instructions
What is an embedded system?
Computer system inside a larger computer system.
What happens in Fetch?
1) Memory address is copied from PC –> MAR.
2) Copy instruction stored in MAR –> MDR.
What happens in Decode?
1) Instruction in the MDR is decoded by the CU.
2) CU may then prepare for the next step e.g. loading values into the MAR or MDR.
What happens in Execute?
1) Instruction is executed.
2) PC is incremented so the CPU can now execute the next instruction in memory.
3) Before a new instruction is incremented, CPU checks for interrupts.