The CPU Flashcards
CPU
Brain if the computer
Processes the data; searching, sorting, calculating and decision making
Made up of main memory, cache memory and processor
Fetch
- Address of next item is put on the address bus
- The data then travels back on the data bus
Decode
ALU decodes the instruction
Hiw the CPU works (1)
An input device sends data to the CPU, the control unit receives this data
How the CPU works (2)
The control unit sends this data to the main memory
How the CPU works (3)
When it is needed, the data is transferred from main memory to cache
How the CPU works (4)
The data is then sent to the ALU for processing
How the CPU works (5)
The data is passed to the control unit which passes it to an output device
MAR
Memory Address Register
Holds the address of the instructions or piece of data to be fetched or stored
MDR
Memory Data Register
Once fetched from memory, the instruction is held here
PC
Program Counter
Stores the address of the next instruction to be fetched
CIR
Current Instruction Register
Holds the current instruction which has been fetched from the MDR
ACC
Accumulator
One of the general purpose registers in which all calculations are carried out
Control unit
- Manages and monitors hardware on the computer to ensure the correct data goes to the correct hardware
- Manages the input and output signals, ensuring these are dealt with correctly
- Manages the fetch, decode, execute cycle
Immediate Access Store
(IAS/ CAS/ Cache)
- Stores the data which is to be immediately processed
- The CPU takes a chunk of data/ instructions from the RAM and keeps it close so that it always has a constant supply of data to process
- If the data/instructions were downloaded from RAM one at a time, the CPU would be slower because the CPU works faster than RAM
