I just got a new Intel CPU, and the specifications say 3.5GHz but with turbo boost to 3.9GHz. What does Intel Turbo Boost do? From the description it sounds like they are saying "The road's speed limit is 100 km/hr, but if you get to that speed then the new speed limit is 140 km/hr". Why not just set the clock speed to 3.9GHz to start with? So what is Intel Turbo Boost actually doing?
Intel® Turbo Boost Technology 2.01 automatically allows processor cores to run faster than the rated operating frequency if they’re operating below power, current, and temperature specification limits. Frequency increases occur in increments of 133 MHz for Nehalem microarchitecture processors and 100 MHz for Sandy/Ivy Bridge microarchitecture processors. When any of the electrical or thermal limits are reached, the operating frequency automatically decreases in decrements of 133 MHz/100 MHz until the processor is again operating within its design limits. 3.5 Ghz in your case is the design limit at which processor can run continuously for long time given the standard cooling is working properly.
Availability and frequency upside of Intel Turbo Boost Technology 2.0 state depends upon a number of factors including, but not limited to the following:
- Type of workload
- Number of active cores
- Estimated current consumption
- Estimated power consumption
- Processor temperature
Intel Turbo Boost Technology 2.0 allows the processor to operate at a power level that is higher than its TDP configuration and data sheet specified power for short durations to maximize performance.
Turbo boost raises the speed when the CPU is capable of it. Intel would love to guarantee you could run at 3.9GHz all the time, but they can't. The CPU might overheat or the current draw might be higher than the packaging can handle. So they guarantee you 3.5GHz and raise the clock to as much as 3.9GHz when they can.
Basically silicon manufacturer rate their processor frequency way less than its actual capability.
Because when CPU work in maximum frequency for very long time there is a possible chance of damage silicon due to over heat. Enabling Turbo boost will not keep frequency stay in the maximum either they switch to lower frequency when ever either workload is less or cpu is getting heated than its specification.