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Questions and Answers
What is the primary function of the ALU during the execution phase?
What must happen to the results of an instruction after execution in the store step?
What role do status flags play in the CPU?
What is the purpose of preparing for the next cycle after the store step?
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Which of the following statements is false regarding data movement in the execution phase?
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What is the primary function of the Memory Address Register (MAR)?
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Which register holds the fetched instruction before it is decoded?
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What is the role of the Status Register (SR)?
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During the Fetch step of the machine cycle, what does the Program Counter (PC) do?
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What occurs during the Decode step of the machine cycle?
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What is the primary function of the control unit in the processor?
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Which register is primarily responsible for temporarily holding data values that are being read from or written to memory?
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What is the purpose of control signals generated after decoding an instruction?
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Which of the following operations is NOT handled by the Arithmetic and Logic Unit (ALU)?
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What does the Program Counter (PC) register store?
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What happens to the Program Counter (PC) during the Fetch step?
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How does the control unit ensure that instructions are executed in the correct order?
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What type of operations includes shifting binary patterns in the ALU?
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Which register holds the instruction currently being executed by the processor?
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Which of the following is NOT a responsibility of the control unit?
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What is the role of general-purpose registers in a processor?
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Study Notes
The System Unit & Processor
- The System Unit houses the main components of a computer system, including the processor, memory, and storage.
The Processor
Control Unit (CU)
- The Control Unit organizes and sequences micro-operations necessary for instruction execution.
- It decodes instructions to determine required actions, such as loading data, performing logic operations, or arithmetic calculations.
- Transmits control signals to and from other components, verifying successful signal delivery and ensuring timely information flow.
- Guarantees that instructions are executed in the correct order.
Arithmetic and Logic Unit (ALU)
- The ALU performs arithmetic and logical operations, including:
- Addition, subtraction, multiplication, and division.
- Logical operations: AND, OR, NOT, and XOR.
- Value comparisons: greater than, less than, equal to.
- Binary pattern shifts (left and right).
Registers
- Registers are high-speed memory locations within the processor used for temporary data storage.
- General-purpose registers hold intermediate results from computations.
- Special-purpose registers are defined below:
- Program Counter (PC): Stores the address of the next instruction to be executed.
- Current Instruction Register (CIR): Holds the currently executing instruction.
- Memory Address Register (MAR): Contains the address of the memory location to access for load or store operations.
- Memory Data Register (MDR): Holds data values or instructions being read from or written to memory.
- Accumulator: Stores results from ALU calculations.
- Status Register (SR): Contains flags indicating the result state of the last instruction and detects errors or exceptions.
Machine Cycle Steps
Fetch
- Involves several sub-steps:
- The PC updates to get the address of the next instruction.
- The CPU sends a memory read request for the address stored in the PC.
- The fetched instruction is loaded into the Instruction Register (IR).
Decode
- Instruction breakdown to identify the opcode and operands.
- Control signals are generated based on the instruction, directing operations of components like the ALU and registers.
Execute
- The ALU performs the specified operations.
- Data movement occurs between registers and memory as required.
- Input/output operations may take place if specified by the instruction.
Store
- Results from execution are written back to the appropriate register or memory.
- Status flags are updated post-execution to reflect the operation's results.
- Prepares the system for the next machine cycle, beginning again with the fetch step.
Conclusion
- Understanding the processor's structure and how it processes instructions (through the fetch-decode-execute-store cycle) is crucial for grasping basic computer architecture concepts.
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Description
Test your knowledge on the System Unit and Processor components. This quiz covers topics such as the Control Unit, its functions, and the overall organization of the processor. Perfect for students looking to deepen their understanding of computer architecture.
