Single-cycle vs a pipelined approach

Question

I understand that single-cycle programs are not very efficient. One reason is because not all instructions are equal in length, but in a single-cycle program, all instructions are completed in the same length of time.

In pipeline, throughput is increased, which means the time between one output and the next will be shorter than in a single-cycle implementation after you reach a certain point. But then can you say that instructions in a pipelined approach take the same amount of time (going from IF/Instruction Fetch to WB/Writeback)? Or is this the wrong conclusion?

Answer 1

See all instructions in a single cycle non pipelined structure do not necessarily take same amount of time rather the next instruction to be executed after an instruction can not start until the next clock cycle ,current instruction may complete before the current cycle because cycle length is determined by the longest instruction.e.g add register completes before load in a RISC.

Now in a pipelined structure processor is
multistage with register to store and propogate the state of processor.Now basically on pipelined processor we save time by overlapping two instructionss' substages.hence even though individually the length of instruction is increased but overall time has reduced.Now see every instruction may not go through all the stages eg load and add again So overall latency for each instruction will consist of all the stages but its execution may have had taken less number of cycles

So you can say that latency of each instruction is same but not the execution time or cycles consumed