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CPU, 3 Main Parts, Von Neumann’s Design, FDE cycle
CPU
1) What does the CPU mean
2) What is the Job of the CPU
1) Central Processing Unit
2) It processes all of the data and instructions that make the system work
What are the 3 main parts of the CPU and their function?
1) Control Unit (CU)
It’s in overall control of the CPU, and its main job is to manage the FDE of program instructions by following the FDE cycle. It controls the flow of data in and out of the CPU.
2) Arithmetic Logic Unit (ALU)
Does all the calculation’s.
Does simple adding and subtracting and compares the size of numbers and can do multiplication and division using repeated addition and subtracting.
It performs logic operations such as AND.OR.NOT and binary shifts. It contains the accumulator.
3) The cache
Slower than registers but faster than RAM
Stores regularly used data so the CPU can access it quickly the next time it’s needed
When the CPU requests data it will check cache and if it’s not there then it will fetch it from RAM.
Low capacity and are expensive compared to RAM and secondary storage.
Von Neumann Architecture
Explain the order of Von Neumanns architecture (4 marks
1) Program Counter (inside the Control Unit)
Holds the memory address of the instruction for each cycle.
2) Registers (MAR)
Holds any memory address about to be used by the CPU.
3) Registers (MDR)
Holds actual data or instruction.
4) Accumulator (inside the ALU)
Stores intermediate results of calculations in the ALU.
Fetch Decode Execute Cycle
Explain the Fetch Stage
1) Copy memory address from the program counter to the MAR.
2) Copy the instruction from the MAR to the MDR.
3) increment the program counter to point to the address of the next instruction ready for the next cycle.
Fetch Decode Execute Cycle
Explain the Decode stage
1) the instruction in the MDR is decoded by the control unit.
2) the control unit prepares for its next step
Fetch Decode Execute Cycle
Explain the execute stage
1) the instruction is preformed
Note
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