A processor with 16 general purpose registers uses a 32-bit instruction…
2024
A processor with 16 general purpose registers uses a 32-bit instruction format. The instruction format consists of an opcode field, an addressing mode field, two register operand fields, and a 16-bit scalar field. If 8 addressing modes are to be supported, the maximum number of unique opcodes possible for every addressing mode is _________
Answer: 32 — Solution: Each register operand field must encode 16 registers, which requires 4 bits per register field (since 2^4 = 16). Two register fields therefore use 8…
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Correct answer: 32
Solution:
Each register operand field must encode 16 registers, which requires 4 bits per register field (since 2^4 = 16). Two register fields therefore use 8 bits total.
The addressing mode field must support 8 modes, which requires 3 bits (since 2^3 = 8).
The scalar field uses 16 bits as given.
Total bits used by registers, addressing mode, and scalar = 8 (registers) + 3 (addressing mode) + 16 (scalar) = 27 bits.
Bits remaining for the opcode = 32 (total instruction bits) - 27 = 5 bits.
Maximum number of unique opcodes possible for every addressing mode = 2^5 = 32.
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