1.1 Systems Architecture Flashcards
Central Processing Unit (CPU)
Brain of the computer system. It processes all the data and instructions which make the system work, and carries out most of the calculations.
What is the function of the CPU?
To fetch, decode, and execute instructions.
What is the fetch execute decode cycle?
It’s the basic operation cycle of a computer. It is the process by which a computer retrieves a program instruction from its memory, determines what actions the instruction requires, and carries out those actions.
Fetch instruction
- Copy memory address from the PC to the MAR.
- Copy the instruction stored in the MAR address to the MDR.
- Increment (increase) the program counter to point the address of the next instruction, ready for the next cycle.
Decode Instruction
The instruction in the MAR is decoded by the CU
Execute Instruction
1) The data at the MAR address is read from RAM
2) The ALU performs any calculations required on the ACC
3) The value in the MDR is written to the address in the MAR
What are the common components of the CPU
- Arithmetic Logic Unit (ALU)
- Control Unit (CU)
- Cache
- Registers
Control Unit (CU)
Decodes instructions and sends signals to control how data moves around the CPU.
Arithmetic Logic Unit (ALU)
Performs all arithmetic operations (for example, addition and subtraction) and all logic operations (such as sorting and comparing numbers)
Cache
Very fast memory in the CPU that stores regularly used data so the CPU can access it quickly the next time its needed.
Registers
- Memory Address Register (MAR)
- Memory Data Register (MDR)
- Program Counter
- Accumulator
Memory Address Register (MAR)
Holds the address of where data or instructions be will be fetched from or stored to.
Memory Data Register (MDR)
Holds the data fetched from, or to be written to, the external memory.
Program Counter (PC)
Holds the memory address of the instruction for each cycle
Accumulator (ACC)
Stores the intermediate results of calculations made by the ALU.
