It means that the clock rate for the CPU runs at 2.5GHz but if a demanding app is using a lot of CPU, it can run at 3.1GHz for short periods of time2.5GHz dual-core Intel Core i5
Turbo Boost up to 3.1GHz
As example, MBA specs say....
2.5GHz dual-core Intel Core i5
Turbo Boost up to 3.1GHz
It means that the clock rate for the CPU runs at 2.5GHz but if a demanding app is using a lot of CPU, it can run at 3.1GHz for short periods of time
Maybe that's the reason why Activity Monitor can show OVER 100% load?
It boots the engines to Warp 10 until Scottie gets on the horn and says:
"Captain! She canna take any more!"
All the Intel CPUs are limited by heat production. The faster the chip runs, and the more work it does, the more heat. And if the heat gets too much and the fans can't take the heat away fast enough, the speed is reduced.
The first number (say 1.7 GHz for some MBA model) means the processor can run all cores at 1.7 GHz 24 hours a day without getting too hot. But if you use only one core for a short time, it can go up to the "Turbo Boost" speed.
K.I.T.T. and K.A.R.R. were both equipped with a Turbo Boost capability. The system consisted of a series of rear mounted undercarriage rocket motors, which allowed the car to accelerate to speeds in excess of 200 mph. The rockets could fire both forwards and backwards as needed.
The system had two secondary uses:
- It could be used to provide power for pushing or pulling heavy objects when necessary.
- When used in combination with the Trajectory Guidance System and a pair of front-mounted rocket motors, the car could "jump" 40 feet into the air to avoid obstacles.
The Turbo Boost capability was used in most episodes of the Original Series.
[/QUOTE source=http://knight-rider.wikia.com/wiki/Turbo_Boost]