Question

(d) 7650 (e) None of the above Question 7 [18 Points]-Instruction Set Architecture (ISA) I. Suppose an instruction set has 32-bit instructions. Every instruction has an 8-bit opcode and a 12- bit immediate operand. Some instructions have three register operands (two sources and a destination register). Every instruction that uses registers must be able to specify any of the registers. How many registers can this instruction set support? (a) 32. (b) 64. (c) 16. (d) There is not enough information given to answer the question. ECE228 Exam-3D pg. 5

Answer 1

Every instruction has 8 bit opcode.

Instruction size is 32 bit.

Immediate operand is 12 bit.

Some instructions have three register operands.

Instruction size - (3×(register operand)+opcode)=immediate operand

=> 32-(3n+8)=12

=>3n+8=20

=>3n=12

=>n=4

Now, the number of registers that the instruction set support is,

2^n =2^4 = 16

Therefore the correct option is (c) 16.