Turbo is usually defined for multi-core processors. With all cores running, you get the default speed, 1.6Ghz in your example. If less cores are used, and CPU demand is high, it will increase the CPU clock speed to provide more compute power to a single core.
This is all based on the heat the CPU generates. Multi core CPU are rated at a clock speed with all cores running and get to a certain amount of heat generated. You cannot exceed that (practically). With less cores running, the CPU can increase the clock speed, causing the CPU to run hotter, but since it is less cores, the total heat dissipation of the CPU is the same (maximum).
It's all a balancing act, automatically built into the CPU. A single core application will tend to run closer to the turbo speed. A multi-core application will tend to force the CPU clock back to its default design speed.