INT 2F U - Microsoft Profiler (PROF.COM/VPROD.386) - START PROFILING
        AX = 4503h
Notes:  Profiling is also turned on by the key combinations
          LeftShift + RightShift + Alt
          LeftShift + RightShift + Ctrl
        for PROF.COM, this call programs the CMOS clock by reading register
          0Ch, and setting bit 6 of register 0Bh.  It then makes sure that IRQ8
          is unmasked