Probably should have been: Why are branch delay slots a bad thing? Branch delay slots were used in early pipelined RISC processors: MIPS, PA-RISC, SPARC. Th

Probably should have been: Why are branch delay slots a bad thing? Branch delay slots were used in early pipelined RISC processors: MIPS, PA-RISC, SPARC. These were short pipelines but not superscalar and not out of order superscalar. Navigating pipeline hazards gets much more complicated with much deeper pipelines, more functional units and out of order execution. Basically, branch delay slots don't scale.