Question

A microprocessor has an increment memory direct instruction, which adds 1 to the value in memory location. The instruction has five stages: fetch opcode (four bus clock cycles); fetch operand address (four bus clock cycles); fetch operand (five bus clock cycles); add 1 to operand (three bus clock cycles) and, store operand (two bus clock cycles). How many bus clock cycles are required to execute the instruction

Answer 1

According to the data given,

Fetch opcode : four bus clock cycles,

fetch operand address : four bus clock cycles,

fetch operand : five bus clock cycles,

add 1 to operand : three bus clock cycles,

store operand : two bus clock cycles.

So, the total number of cycles taken to execute the instruction are 4 + 4 + 5 + 3 + 2 = 18 bus clock cycles.

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