RISC & CISC: Evaluating Expression X
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Questions and Answers

What is the primary issue with the accumulator architecture?

  • It has an intrinsic performance problem. (correct)
  • It cannot perform multiplication operations.
  • It requires a large number of registers.
  • It is not suitable for RISC processors.

    • Which of the following logic gates is used to implement binary multiplication with 'shift left' and additions?

  • NAND
  • OR
  • NOT
  • AND (correct)

    • What is the purpose of the 1-bit multiplexer circuit shown in Fig. 2.5?

  • To implement binary multiplication.
  • To select between two input signals. (correct)
  • To perform addition operations.
  • To perform subtraction operations.

    • How many instructions are required to implement the expression 'X' in the accumulator architecture?

    <p>19</p> Signup and view all the answers

    What is the primary advantage of the RISC architecture over the CISC architecture?

    <p>RISC has a smaller instruction set.</p> Signup and view all the answers

    What is the purpose of the 4-bit adder circuit shown in Fig. 2.4?

    <p>To perform addition operations.</p> Signup and view all the answers

    Which phase of the instruction cycle is responsible for executing the instruction?

    <p>Effective instruction execution.</p> Signup and view all the answers

    What is the expression implemented by the pseudo-code in Listing 2.7?

    <p>(C - D) × (A + B) - (E × F)</p> Signup and view all the answers

    What is the primary function of the accumulator in the processor architecture depicted in Figure 2.3?

    <p>Arithmetic and logical operations</p> Signup and view all the answers

    What type of instruction set architecture is implied by the microprogram in Figure 2.3?

    <p>RISC (Reduced Instruction Set Computing)</p> Signup and view all the answers

    What is the purpose of the IR register in the microprogram?

    <p>Stores the opcode for the current instruction</p> Signup and view all the answers

    What is the function of the logic gate in the binary arithmetic circuit?

    <p>Performs logical operations on binary numbers</p> Signup and view all the answers

    What is the purpose of the DR register in the microprogram?

    <p>Stores the data fetched from memory</p> Signup and view all the answers

    What is the effect of the instruction #16 Jump if positive on the program counter?

    <p>The program counter is set to the address specified in the instruction</p> Signup and view all the answers

    What is the primary function of the Accumulator (ACC) in the given microprogram?

    <p>To perform arithmetic operations</p> Signup and view all the answers

    What is the main difference between RISC and CISC architectures?

    <p>RISC uses a fixed instruction length, while CISC uses a variable instruction length</p> Signup and view all the answers

    What is the primary purpose of the Address Register (AR) in the given microprogram?

    <p>To manage memory addresses</p> Signup and view all the answers

    What is the function of the logic gate in the binary arithmetic circuit?

    <p>To make decisions based on input conditions</p> Signup and view all the answers

    What is the purpose of the case 15 instruction in the microprogram?

    <p>To jump to a specified address</p> Signup and view all the answers

    What is the role of the Data Register (DR) in the microprogram?

    <p>To hold the data temporarily</p> Signup and view all the answers

    What is the function of the case 21 instruction in the microprogram?

    <p>To halt the processor</p> Signup and view all the answers

    What is the purpose of the binary arithmetic circuit?

    <p>To perform arithmetic operations</p> Signup and view all the answers

    In the accumulator-based architecture, what is the primary function of the ACC register?

    <p>To perform arithmetic operations and hold the result</p> Signup and view all the answers

    In the load-store architecture, what is the purpose of the data register (DR)?

    <p>To store the data temporarily during load and store operations</p> Signup and view all the answers

    What is the purpose of the instruction register (IR) in the microprogram?

    <p>To decode the instruction opcode</p> Signup and view all the answers

    In the microprogram representation, what is the purpose of the switch statement?

    <p>To dispatch the correct micro-operation based on the opcode</p> Signup and view all the answers

    What is the addressing mode used in the instruction 'LOAD'?

    <p>Register indirect addressing</p> Signup and view all the answers

    What is the effect of the instruction 'JUMP IF POSITIVE' on the program counter?

    <p>The program counter is set to the address field value only if the accumulator is positive</p> Signup and view all the answers

    What is the primary advantage of using a microprogram representation?

    <p>It makes it easier to design and implement complex instruction sets</p> Signup and view all the answers

    In the accumulator-based architecture, which register holds the memory address during the execution of an instruction?

    <p>Address Register (AR)</p> Signup and view all the answers

    What is the role of the address register (AR) in the microprogram?

    <p>To hold the address field value of the instruction</p> Signup and view all the answers

    What is the primary advantage of the load-store architecture over the accumulator-based architecture?

    <p>More efficient use of memory</p> Signup and view all the answers

    In the microprogram representation, what is the function of the Instruction Register (IR)?

    <p>Decodes the opcode</p> Signup and view all the answers

    Which addressing mode is implied by the microprogram in Figure 2.3?

    <p>Direct addressing</p> Signup and view all the answers

    What is the purpose of the Data Register (DR) in the microprogram?

    <p>Stores the data operands</p> Signup and view all the answers

    Which of the following is a characteristic of the accumulator-based architecture?

    <p>Uses a single accumulator register for all operations</p> Signup and view all the answers

    In the accumulator-based architecture, which register is responsible for storing the address of the memory location to be accessed?

    <p>Address Register (AR)</p> Signup and view all the answers

    What is the primary difference between the accumulator-based architecture and the load-store architecture?

    <p>The way data is accessed and stored</p> Signup and view all the answers

    What is the purpose of the Instruction Register (IR) in the microprogram?

    <p>To store the instruction being executed</p> Signup and view all the answers

    What type of addressing mode is used in the microprogram representation shown in Fig. 2.3?

    <p>Indirect addressing</p> Signup and view all the answers

    What is the function of the Data Register (DR) in the accumulator-based architecture?

    <p>To store the data being processed</p> Signup and view all the answers

    What is the role of the Program Counter (PC) in the microprogram?

    <p>To keep track of the current instruction being executed</p> Signup and view all the answers

    Study Notes

    Processor Operation and Instructions

    • The given pseudo-code in Listing 2.7 is equivalent to the expression: (C − D) × (A + B) − (E × F) / (H − I) × (F + G)
    • The expression can be implemented using a 4-bit adder circuit, 1-bit multiplexer, and binary multiplication with "shift left" and additions.

    Logic Gates

    • Basic logic gates used to implement circuits include:
      • AND gate
      • NOT gate
      • NAND gate
    • Truth tables are provided for these gates in Figures 2.6 to 2.8.

    Phases of Processor Operation

    • The processor operation consists of five phases:
      • Operation code fetch
      • Operation code decode
      • Operands fetch
      • Effective instruction execution
      • Results store

    Accumulator Architecture

    • The accumulator architecture has an intrinsic performance problem.
    • The accumulator code version implementing the expression "X" is shown in Listing 2.8.
    • The code has 19 instructions.

    Microprogram

    • The microprogram related to the processor with accumulator architecture is shown in Figure 2.3.
    • The microprogram behaves as follows:
      • Verify the operation code to execute
      • Execute the corresponding operation (LOAD, STORE, ADDITION, JUMP, JUMP IF POSITIVE, STOP)

    Microprogram Pseudo-Code

    • The microprogram pseudo-code is shown in Listing 2.5 and 2.6.
    • The code includes instructions for:
      • LOAD operation
      • STORE operation
      • ADDITION operation
      • JUMP operation
      • JUMP IF POSITIVE operation
      • STOP operation

    Microprogram Pseudo-Code

    • The microprogram pseudo-code has a switch statement that verifies the operation code to execute based on the instruction register (IR).
    • There are several cases in the switch statement, each corresponding to a specific operation:

      LOAD Operation

      • Case 1: AR (address register) gets the address field from DR (data register).
      • DR gets the contents of memory at the address indexed by AR.
      • ACC (accumulator register) gets the value from DR.

      STORE Operation

      • Case 2: AR gets the address field from DR.
      • DR gets the accumulator value.
      • Memory position indexed by AR gets the value from DR.

      ADDITION Operation

      • Case 5: AR gets the address field from DR.
      • DR gets the contents of memory at the address indexed by AR.
      • ACC gets the sum of the accumulator value and DR value.

      JUMP Operation

      • Case 15: PC (program counter) gets the address field value from DR.

      JUMP IF POSITIVE Operation

      • Case 16: If the accumulator value is greater than zero, PC gets the address field value from DR.

      STOP Operation

      • Case 21: The processor halts.

    Microprogram Pseudo-Code Example (Listing 2.7)

    • The example consists of several operations:

      STORE Operation

      • AR gets the PC value.
      • AR gets the address field from DR.
      • DR gets the accumulator value.
      • Memory position indexed by AR gets the value from DR.

      ADDITION Operation

      • IR gets the opcode from DR.
      • AR gets the address field from DR.
      • DR gets the contents of memory at the address indexed by AR.
      • ACC gets the sum of the accumulator value and DR value.

      JUMP Operation

      • PC gets the address field value from DR.

      JUMP IF POSITIVE Operation

      • If the accumulator value is greater than zero, PC gets the address field value from DR.

      STOP Operation

      • The processor halts.

    Microprogram and Processor Architecture

    • The microprogram represents the processor with accumulator architecture.
    • The processor consists of:
      • Data Register (DR)
      • Address Register (AR)
      • Program Counter (PC)
      • Instruction Register (IR)
      • Arithmetic Logic Unit (ALU)
      • Memory
      • Control Unit

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    Description

    Simplify the given pseudo-code to evaluate the expression X. The code involves operations on variables A, B, C, D, E, F, G, H, and I. Evaluate the expression X and simplify it.

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