Intel processors have never been simple, but they definitely used to be simpler. In the endless journey to provide more performance, successive generations of CPUs have brought higher frequencies and more cores. As frequencies leveled off, however, other methods to increase performance emerged with various technologies that dynamically alter the speed of the processor (i.e., give it a “boost”). As this is a topic that is often misunderstood, it seemed like a good idea to provide a brief overview.
The definition of the base frequency has evolved over the years, but these days it refers to the guaranteed clock speed a CPU can maintain with full utilization within predefined heat and power limitations (and does not rely on any sort of boosting technology). While base frequencies used to be fixed, CPUs now routinely underclock themselves automatically to conserve power and stay cool, and then increase to a higher frequency quickly when needed—but only as high as their stated base frequency. To go higher, you need a boost.
Max Turbo Frequency
When people mention the boost clock of a processor, this is typically what they’re referring to. The max turbo frequency is the maximum frequency at which the processor is capable of operating using Intel® Turbo Boost Technology 2.0. This gives a burst of speed to a core or group of cores, and depends on a variety of factors.1 Processors routinely enter and exit “boost mode” automatically throughout various computing tasks. Although Intel provides the max turbo frequency of only a single core in a CPU’s specs, all active cores can get a boost as well, and the frequency at which they boost tends to go down slightly as you add cores, and maintains the same frequency across all of them. One notable exception to this would be Intel’s current flagship processor, the i9-9900KS, which provides a boost clock of 5.0 GHz across all 8 cores consistently. Compare this to their previous flagship, the i9-9900K, in the tables below.