Take three bubbles?

Back-to-back dependence is too frequent

Solution: Hardware bypass paths

Allow the ALU to bypass the produced value in time: not always possible

Data Dependence

Need a live bypass! (requires some negative time travel: not yet feasible in real world)

No option but to take one bubble

Bigger Problems: load latency is often high; you may not find the data in cache

Structural Hazard

Usual solution is to put more resources