Pentium 4s ten years ago could hit around 4 GHz.  Running any faster than that runs into some issues with the basic physics.  Some good explanations here[1].
Now we&#x27;re into the era of &quot;well, that&#x27;s as fast as we can go on one core, let&#x27;s chuck more cores at it&quot;.  Except writing parallel code is hard, and parallelism doesn&#x27;t help if what you&#x27;re doing is effectively single-threaded.  Great for mass processing of vertex data in a 3D mesh<p>The next frontier was faster caches and memory, so we could keep those processors burning at max speed more of the time, with fewer idles waiting on input or output.  Then we needed faster main storage, so we could spend less time fetching data from slow spinning disks into our limited, fast memory.  Voila, SSDs.  Now we&#x27;re down to fast CPUs, fast caches, fast memory, fast disks, and slow networking.  Someday we&#x27;ll get wide-spread fiber deployed, and that gate becomes less of a problem.<p>Through all of this, the effective speed of computers has continued to rise, although the top-line limit of CPU Hz hasn&#x27;t changed much.<p>[1] <a href="http:&#x2F;&#x2F;electronics.stackexchange.com&#x2F;questions&#x2F;122050&#x2F;what-limits-cpu-speed" rel="nofollow">http:&#x2F;&#x2F;electronics.stackexchange.com&#x2F;questions&#x2F;122050&#x2F;what-l...</a>