Computer Architecture: Fetch Cycle Registers
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Questions and Answers

What does the instruction decoding process involve?

  • Performing arithmetic calculations
  • Setting the instruction cycle code
  • Generating a sequence of micro-operations based on the opcode (correct)
  • Loading data into memory

    • The indirect cycle is always followed by the fetch cycle.

    False

    What are the four states represented by the instruction cycle code (ICC)?

    Fetch, Indirect, Execute, Interrupt

    The component responsible for performing arithmetic and logic operations is called the __________.

    <p>ALU</p> Signup and view all the answers

    Match the following processor components with their functions:

    <p>ALU = Performs arithmetic and logic operations Registers = Stores data temporarily Internal Data Paths = Move data within the processor Instruction Cycle Code (ICC) = Indicates current state of instruction cycle</p> Signup and view all the answers

    Which micro-operation occurs first when executing an ADD instruction?

    <p>MAR  (IR(address))</p> Signup and view all the answers

    Registers are used for permanent storage of data within the processor.

    <p>False</p> Signup and view all the answers

    What sequence of micro-operations would likely follow the loading of the address into the MAR?

    <p>MBR  Memory, R1  (R1) + (MBR)</p> Signup and view all the answers

    What is the role of control signals in a processor?

    <p>They act as commands issued by the control unit to manage component activities.</p> Signup and view all the answers

    Control words are collections of bits used to activate specific processor control lines.

    <p>True</p> Signup and view all the answers

    What is the purpose of the system bus in a processor?

    <p>The system bus serves as a communication pathway allowing the control unit to interact with memory and I/O modules.</p> Signup and view all the answers

    The control unit directs the flow of data and operations using _____ signals.

    <p>control</p> Signup and view all the answers

    Match the following components with their functions:

    <p>Control Unit = Issues control signals System Bus = Communication pathway Control Word = Activates specific control lines Control Signals = Manage component activities</p> Signup and view all the answers

    What is the primary function of the control unit in a processor?

    <p>Overseeing and controlling operations</p> Signup and view all the answers

    The control signals generated by the control unit are only used for external communication.

    <p>False</p> Signup and view all the answers

    Name one method used to implement the tasks of the control unit.

    <p>Hardwired control or microprogrammed control.</p> Signup and view all the answers

    The control unit determines the ________ of micro-operations.

    <p>sequencing</p> Signup and view all the answers

    Which of the following is NOT a type of control signal?

    <p>Memory allocation signal</p> Signup and view all the answers

    Match the types of control signals with their functions:

    <p>ALU activation signal = Instructs the ALU to perform functions Data path signal = Controls the internal flow of data External bus signal = Coordinates communication with external devices</p> Signup and view all the answers

    Which component communicates with external modules using external data paths?

    <p>System Bus</p> Signup and view all the answers

    Describe one function of the control unit related to instruction execution.

    <p>Activating the necessary control signals to execute each micro-operation.</p> Signup and view all the answers

    What is the primary role of clock pulses in the control unit's operations?

    <p>To provide a regular timing mechanism</p> Signup and view all the answers

    The control unit has direct access to the data being processed.

    <p>False</p> Signup and view all the answers

    What does the control unit rely on to make decisions about controlling operations?

    <p>Pre-programmed knowledge and predefined rules.</p> Signup and view all the answers

    The control unit is considered _____ because it operates with limited visibility of actual results.

    <p>minimal</p> Signup and view all the answers

    Match the function with its corresponding description:

    <p>Clock Pulses = Provide timing for events Control Unit = Orchestrates instruction execution Micro-operations = Basic tasks performed during processing Instructions = Commands for the processor</p> Signup and view all the answers

    Which register holds the address of the next instruction to be fetched?

    <p>Program Counter (PC)</p> Signup and view all the answers

    What is one significant aspect of the control unit's operation?

    <p>Issues control signals</p> Signup and view all the answers

    The control unit's minimal access to data limits its functionality in a computer.

    <p>False</p> Signup and view all the answers

    The Memory Buffer Register (MBR) contains the address of the next instruction to be executed.

    <p>False</p> Signup and view all the answers

    How do clock pulses contribute to the instruction cycle?

    <p>They ensure orderly progression and prevent conflicts.</p> Signup and view all the answers

    What is the first step in the Fetch cycle?

    <p>Move the address of the next instruction from the program counter (PC) to the memory address register (MAR).</p> Signup and view all the answers

    In the Indirect cycle, the instruction's address field is first transferred to the _______.

    <p>MAR</p> Signup and view all the answers

    Match the register with its function:

    <p>MAR = Holds the address of memory for read/write operations MBR = Contains value to be stored or last value read PC = Holds the address of the next instruction IR = Holds the last instruction fetched</p> Signup and view all the answers

    What happens during the Interrupt cycle?

    <p>The address of the interrupt routine is stored in the PC.</p> Signup and view all the answers

    The Execute cycle has a fixed sequence of micro-operations.

    <p>False</p> Signup and view all the answers

    What must occur if an instruction specifies an indirect address?

    <p>An indirect cycle must precede the execute cycle.</p> Signup and view all the answers

    What is the primary role of control signals emitted by the control unit?

    <p>To initiate specific micro-operations</p> Signup and view all the answers

    The control unit does not need to track its position in the instruction cycle.

    <p>False</p> Signup and view all the answers

    What signals does the control unit send to read a word from memory into the MBR?

    <p>A control signal that opens gates for the MAR onto the address bus, a memory read control signal on the control bus, a signal for data bus storage in MBR, and signals to increment the PC.</p> Signup and view all the answers

    The control unit opens the gates between the PC and the _____ during the fetch cycle.

    <p>MAR</p> Signup and view all the answers

    Match the following components with their functions during the fetch cycle:

    <p>PC = Holds the address of the next instruction MAR = Stores the address to be accessed in memory MBR = Holds the data read from memory IR = Holds the instruction that is currently being executed</p> Signup and view all the answers

    What happens first in the fetch cycle?

    <p>The contents of the PC are transferred to the MAR</p> Signup and view all the answers

    The control unit can perform indirect cycles without examining the IR.

    <p>False</p> Signup and view all the answers

    How does the control unit maintain knowledge of its position in the instruction cycle?

    <p>It uses its internal state information to track the current stage of the instruction cycle.</p> Signup and view all the answers

    Study Notes

    Fetch Cycle Registers

    • Memory Address Register (MAR): Connects to the system bus's address lines, specifying memory address for read/write operations.
    • Memory Buffer Register (MBR): Connects to the data lines of the system bus, containing the value to be stored in memory or the last value read.
    • Program Counter (PC): Holds the address of the next instruction to be fetched.
    • Instruction Register (IR): Holds the last fetched instruction.

    Fetch Cycle Steps and Micro-operations

    • Step 1: The address of the next instruction is moved from the Program Counter (PC) to the Memory Address Register (MAR).
    • Step 2: The instruction is read from memory (at the address in MAR) and stored in the Memory Buffer Register (MBR). Simultaneously, the Program Counter (PC) is incremented to prepare for the next instruction fetch.
    • Step 3: The instruction is moved from the Memory Buffer Register (MBR) to the Instruction Register (IR).

    Indirect Cycle Steps

    • If an instruction specifies an indirect address, an indirect cycle precedes the execute cycle.
    • The address field of the instruction is transferred to the Memory Address Register (MAR).
    • The address of the operand is fetched using the MAR.
    • The address field of the Instruction Register (IR) is updated from the Memory Buffer Register (MBR), changing it from indirect to direct.
    • The IR is now ready for the execute cycle.

    Interrupt Cycle Steps and Micro-operations

    • To handle an interrupt, the processor saves the contents of the Program Counter (PC) into the Memory Buffer Register (MBR).
    • The memory buffer address is stored in the Memory Address Register (MAR).
    • The control unit loads the interrupt routine address into the Program Counter (PC).
    • Then, the CPU processes the interrupt and continues with the instruction cycle.

    Execute Cycle Differences

    • The execute cycle doesn't have a fixed micro-operation sequence like the fetch, indirect, and interrupt cycles, due to the variety of opcodes.
    • The control unit decodes the opcode to determine the specific sequence of micro-operations.
    • This dynamic sequence is dependent on the instruction currently being executed

    Processor Functional Elements

    • Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations.
    • Registers: Temporary storage for data inside the processor.
    • Internal Data Paths: Pathways for data transfer between internal components.
    • External Data Paths: Connections linking registers to external devices (e.g., memory).
    • Control Unit: Manages and directs all operations within the processor.

    Control Unit Tasks

    • Sequencing: Determines the order of micro-operations.
    • Execution: Activating the necessary control signals for each micro-operation.

    Control Signals

    • Control signals are electrical signals activating ALU functions, controlling data pathways, and interacting with external interfaces.
    • Data path, ALU, system bus control lines are different types.
    • Control signals control data transfers and operations inside the processor.

    Control Unit's Fetch Cycle

    • The control unit monitors cycles and maintains an internal state to know its position within the instruction cycle.
    • The control unit emits signals to perform tasks like reading from memory, updating the Program Counter (PC), and transferring data.

    Control Unit in a Computer

    • The control unit manages and synchronizes all processor components and operations.
    • It ensures that micro-operations happen at correct times, preventing conflicts.
    • It acts as the central command center.

    Control Unit's Decision-Making

    • Control unit decisions are made without physically observing results but based on pre-programmed logic.
    • Understanding instruction sets and expected results drive control signal generation to initiate the correct micro-operations necessary for proper execution.

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    Description

    Explore the essential components of the fetch cycle in computer architecture, including the Memory Address Register (MAR), Memory Buffer Register (MBR), Program Counter (PC), and Instruction Register (IR). This quiz covers their functions, steps involved in the fetch cycle, and how they interact during instruction fetching in a CPU. Test your knowledge on the fundamental aspects of CPU operations.

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