clock.cs

 internal static class Program
    {
        [DllImport("Kernel32.dll")]
        private static extern bool QueryPerformanceFrequency(out long lpFrequency);
        [DllImport("Kernel32.dll")]
        private static extern bool QueryPerformanceCounter(out long lpPerformanceCount);

        private static void Main(string[] args)
        {
            long frequency, start, stop;
            double multiplier = 1000 * 1000 * 1000;//nano
            if (QueryPerformanceFrequency(out frequency) == false)
            {
                throw new Win32Exception();
            }

            Process.GetCurrentProcess().ProcessorAffinity = new IntPtr(1);
            const int gigahertz = 1000 * 1000 * 1000;
            const int knownInstructionsPerLoop = 1;

            int iterations = int.MaxValue;
            int g = 0;

            QueryPerformanceCounter(out start);
            for (var i = 0; i < iterations; i++)
            {
                g++;
                g++;
                g++;
                g++;
            }
            QueryPerformanceCounter(out stop);

            var normalTicksPerSecond = frequency * 1000;
            var ticks = (double)(stop - start);
            var time = (ticks * multiplier) / frequency;
            var loopsPerSec = iterations / (time / multiplier);
            var instructionsPerLoop = normalTicksPerSecond / loopsPerSec;

            var ratio = (instructionsPerLoop / knownInstructionsPerLoop);
            var actualFreq = normalTicksPerSecond / ratio;

            Console.WriteLine("Perf counhter freq: {0:n}", normalTicksPerSecond);
            Console.WriteLine("Loops per sec:      {0:n}", loopsPerSec);
            Console.WriteLine("Perf counter freq div loops per sec: {0:n}", instructionsPerLoop);
            Console.WriteLine("Presumed freq: {0:n}", actualFreq);
            Console.WriteLine("ratio: {0:n}", ratio);
        }
    }