I am studying for my exam tomorrow and I am having difficulty in the below code :
sub $2, $1, $3 and $12, $2, $5 or $13, $6, $2 add $14, $2, $2 sw $15, 100($2)
Due to the ALU-ALU dependency here on Register $2 , The sub instruction does not write its result until the fifth stage, meaning that we would have to waste three clock cycles in the pipeline. My question is why 3 clock cycles ? This dependency can be solved by inserting two nops and therefore we are wasting 2 clock cycles ? Please clarify it to me as I am trying to relate the nops to the wasted cycles and I am sure that I have a huge misunderstanding here .