A partial data path of a processor is given in the figure, where RA, RB, and RZ are 32-bit registers

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GATE-CS is a competitive examination conducted in India. This question is from the 2025 GATE-CS Computer Organization and Architecture paper.

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Question

A partial data path of a processor is given in the figure, where RA, RB, and RZ are 32-bit registers. Which option(s) is/are CORRECT related to arithmetic operations using the data path as shown?

Accepted Answer

Correct Answer: (A), (B), and (C)Concept — Processor Data Path with Multiplexers: The data path described contains two multiplexers (MUX) feeding the two ALU inputs, and the ALU output is stored in register RZ.MUX A: selects between a register value (from RA or RB) and an immediate value for ALU Input 1.MUX B: selects between a register value and an immediate value for ALU Input 2.Since each MUX can independently select either a register or an immediate value, the ALU can receive any combination of register and immediate operands:MUX A selectsMUX B selectsOperation typeExampleRegister (RA)Register (RB)Register–RegisterADD RA, RB → RZRegister (RA)Immediate (#n)Register–ImmediateADD RA, #5 → RZImmediate (#m)Register (RB)Immediate–RegisterSUB #10, RB → RZImmediate (#m)Immediate (#n)Immediate–ImmediateADD #3, #4 → RZConclusions:Option A (TRUE): Both MUXes select registers → register-register operation.Option B (TRUE): One MUX selects a register, the other an immediate → register-immediate operation.Option C (TRUE): Both MUXes select immediate values → immediate-immediate operation.Option D (FALSE): The data path is NOT limited to register-immediate only; it supports all three combinations above.

A partial data path of a processor is given in the figure, where RA, RB, and RZ are 32-bit registers. Which option(s) is/are CORRECT related to arithmetic operations using the data path as shown?

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A partial data path of a processor is given in the figure, where RA, RB, and RZ are 32-bit registers. Which option(s) is/are CORRECT related to arithmetic operations using the data path as shown?

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