Computer Science 0.0 / 5 ? ComputingStructure and Function of a ProcessorA2/A-levelOCR Created by: qhtCreated on: 21-08-23 21:23 What is a Program Counter (PC)? A register that tracks the RAM address of the next instruction to be fetched. 1 of 21 What is the Memory Address Register (MAR)? A register that tracks the RAM address of data that is currently being accessed 2 of 21 What is the Memory Data Register (MDR)? MDR stores the data that is transferred from RAM to the CPU 3 of 21 What is the Current Instruction Register (CIR)? A register that stores the instruction that has been fetched from RAM, and is about to be decoded or executed 4 of 21 What is the Accumulator (ACC)? The ACC stores the result of executions performed in the FDE cycle 5 of 21 What is a register? A register is a small storage space for temporary data in the CPU. 6 of 21 What happens in the FDE cycle? Instructions are fetched from RAM, decoded (understood) and executed (processed) by the CPU. 7 of 21 (The FDE Cycle) 1. The PC register displays the address in RAM of the next instruction to be processed. The value is copied into the Memory Address Register (MAR) 8 of 21 2. The PC register is increased by 1. This prepares the CPU for the next instruction to be fetched. 9 of 21 3. The CPU checks the address in RAM which matches the address held in the MAR. 10 of 21 4. The instruction in RAM is transferred to the Memory Data Register (MDR) 11 of 21 5. The instruction in the MDR is copied into the Current Instruction Register (CIR). 12 of 21 6. The instruction in the CIR is decoded (understood) and executed (processed) Any result of an execution is stored in the accumulator (ACC) register. 13 of 21 7. The cycle repeats by returning the first step and checking the program counter for the address of the next instruction 14 of 21 What are the three types of buses? Address Bus - Sends a memory address of where data is stored. The address is sent from the CPU to RAM in the FDE cycle. Data Bus - Transfers data between components. Data is sent both ways. Control Bus - Sends control signals from the control unit to ot 15 of 21 What factors effect the performance of a CPU? Number of cores Cache size Clock speed 16 of 21 Von Neumann Architecture CPU contains what? One control unit One ALU Special registers Data and instructions are stored in the same format in the same area in memory. Data and instructions are transferred across buses (pathways) 17 of 21 Harvard architecture contains what? One control unit One ALU Data and instructions are stored in separate areas in memory Data and instructions are also transferred across buses (pathways) 18 of 21 Define 'buses' A set of parallel wires which connect two or more components inside the CPU 19 of 21 Advantages of Von Neumann Architecture Cheaper to develop as the control unit is easier to design Programs can be optimized in size 20 of 21 Advantages of Harvard Architecture Quicker execution as data and instructions can be fetched in parallel. Memories can be different sizes, which can make more efficient use of space 21 of 21
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