how to turbo off？

[Reihold-Chen]

A/M This is the ratio of the APERF and MPERF ratios exposed in an MSR. For details, see the Intel SDM Vol 3, but basically APERF is a free running counter of actual cycles (i.e., varying with the CPU frequency), while MPERF counts at a constant rate, usually the processor's nominal frequency. A ratio of 1.0 therefore means that the CPU was is running, on average, at the nominal frequency during the test (I had turbo off, that's why you see 1.00 everywhere). Lower than 1 means lower than nominal frequencies (e.g., due to running heavy AVX code).

I want to know how can turbo off ? thank you very much : )