If the IFFlush signal is set which action will be performed

If the IF.Flush signal is set, which action will be performed? *Currently: Caution with this! You can \"nop\" an instruction ONLY if it didn\'t start a stage yet.

a) It will \"nop\" the instruction currently* in the IF stage

b) It will \"nop\" the instruction currently* in the EX stage

c) It will \"nop\" the instruction currently* in the WB stage

d) It will \"nop\" the instruction currently* in the ID stage

Solution

Please follow the data and description :

Flushing the Instructions :

In general a flush one instruction is used in its IF stage if and only if the previous instruction is BEQ and its two source registers are equal. We can flush an instruction from the IF stage by replacing it in the IF/ID pipeline register with a harmless nop instruction. Flushing introduces a bubble into the pipeline, which represents the one cycle delay in taking the branch.

So this goes with the IF stage only.

So the answer is OPTION A (It will \"nop\" the instruction currently* in the IF stage).

Hope this is helpful.