IIRC, part of the GHz problem is that very long pipelines like that of the Pentium 4 tend to show increasing benefits at higher clocks. If you can keep the pipe

IIRC, part of the GHz problem is that very long pipelines like that of the Pentium 4 tend to show increasing benefits at higher clocks. If you can keep the pipeline full then the system reaps the benefits. Sort of like a drag racer - goes very fast in a straight line but terrible on corners. But with longer pipelines comes larger penalties when the pipeline needs to be flushed, so the P4 eventually hit a wall and Intel returned to the late Pentium 3 Tualatin core, refining it into the Pentium M which later evolved into the first Core CPUs.