Uses RDTSC processor instruction in a tight loop to measure how
much time it takes for CPU to churn a million clock ticks. Then
computes clock rate in GHz from this.


== Build


    $ curl -O https://raw.githubusercontent.com/ITikhonov/ghz-osx/master/clockspeed.c
    $ make clockspeed
    cc     clockspeed.c   -o clockspeed

== Run

    $ ./clockspeed 
    1.4 GHz