Superscalar
Although there might not be any interdependent instructions in the list, a superscalar processor still has to check for them, because there's no way to be sure there aren't any unless it checks, and if a dependency is missed the results will be wrong. No matter how fast the processor is, this limits how many instructions can be run at the same time. Checking for dependencies gets harder and harder, even while improvements in hardware manufacturing allow for more execution units in each CPU core.