Consider the following MIPS instruction:  beq $t1, $t1, label What is the ALUSrc control signal value: top or bottom? What is the MemtoReg control signal value: top or bottom? What is the PCSrc control signal value: top or bottom?

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Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
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Chapter1: Introduction
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Consider the following MIPS instruction:  beq $t1, $t1, label

    1. What is the ALUSrc control signal value: top or bottom?
    2. What is the MemtoReg control signal value: top or bottom?
    3. What is the PCSrc control signal value: top or bottom?
This diagram represents a basic single-cycle CPU architecture commonly used in educational settings to demonstrate instruction execution in a processor.

**Diagram Components:**

1. **PC (Program Counter):** 
   - Holds the address of the next instruction to be executed. The PC feeds into the Instruction Memory.

2. **Instruction Memory:**
   - Reads the address from the PC and outputs the corresponding instruction.

3. **Registers:**
   - Comprises a collection of registers for storing temporary data and control information. The diagram indicates paths for reading and writing data.

4. **Adder Components:**
   - There are multiple adders used to compute addresses:
     - One adds a constant (4) to the PC to point to the next instruction.
     - Another calculates the branch target address.

5. **Multiplexers (Mux):**
   - Control data flow based on control signals (e.g., PCSrc, MemtoReg, ALUSrc).
   - Choose between two inputs and forward only one to the output.

6. **ALU (Arithmetic Logic Unit):**
   - Performs arithmetic or logic operations based on control signals. It receives inputs from registers and either outputs a result or triggers a zero indicator for branching.

7. **Sign-extend:**
   - Extends smaller bit-width data to a larger width, typically used for sign extension of immediate values.

8. **Shift Left 2:**
   - Performs bitwise left-shift on input data, commonly used in calculating branch target addresses.

9. **Data Memory:**
   - Used for reading and writing data based on instruction type (e.g., load/store instructions).

10. **Control Signals:**
    - Include RegWrite, MemWrite, MemRead, MemtoReg, ALUSrc, and PCSrc, determining actions such as writing or reading data to/from memory or choosing data paths.

**Operation:**
- The PC fetches the instruction, which is then decoded to determine its type and nature.
- Based on the interpretation, values are read from or written to registers.
- The ALU performs necessary computations, which may include calculations or logic operations.
- Data may be accessed from memory if required.
- The result is then either stored back in the registers, written to memory, or used to modify the PC for the next instruction.

This architecture is a fundamental concept for understanding the functioning of CPUs in computers, illustrating the flow and transformation of data throughout a processor cycle.
Transcribed Image Text:This diagram represents a basic single-cycle CPU architecture commonly used in educational settings to demonstrate instruction execution in a processor. **Diagram Components:** 1. **PC (Program Counter):** - Holds the address of the next instruction to be executed. The PC feeds into the Instruction Memory. 2. **Instruction Memory:** - Reads the address from the PC and outputs the corresponding instruction. 3. **Registers:** - Comprises a collection of registers for storing temporary data and control information. The diagram indicates paths for reading and writing data. 4. **Adder Components:** - There are multiple adders used to compute addresses: - One adds a constant (4) to the PC to point to the next instruction. - Another calculates the branch target address. 5. **Multiplexers (Mux):** - Control data flow based on control signals (e.g., PCSrc, MemtoReg, ALUSrc). - Choose between two inputs and forward only one to the output. 6. **ALU (Arithmetic Logic Unit):** - Performs arithmetic or logic operations based on control signals. It receives inputs from registers and either outputs a result or triggers a zero indicator for branching. 7. **Sign-extend:** - Extends smaller bit-width data to a larger width, typically used for sign extension of immediate values. 8. **Shift Left 2:** - Performs bitwise left-shift on input data, commonly used in calculating branch target addresses. 9. **Data Memory:** - Used for reading and writing data based on instruction type (e.g., load/store instructions). 10. **Control Signals:** - Include RegWrite, MemWrite, MemRead, MemtoReg, ALUSrc, and PCSrc, determining actions such as writing or reading data to/from memory or choosing data paths. **Operation:** - The PC fetches the instruction, which is then decoded to determine its type and nature. - Based on the interpretation, values are read from or written to registers. - The ALU performs necessary computations, which may include calculations or logic operations. - Data may be accessed from memory if required. - The result is then either stored back in the registers, written to memory, or used to modify the PC for the next instruction. This architecture is a fundamental concept for understanding the functioning of CPUs in computers, illustrating the flow and transformation of data throughout a processor cycle.
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