Limit processor speed like in Windows

In Windows (Linux too), you have the very useful "Power saver" mode that limits the maximum frequency at which your CPU runs.

Is there something similar in OS X?

No. OS X doesn't have a CPU or even GPU throttling lever that users can toggle.

There is a nice app, gfxCardStatus to know which of the two GPU is engaged on Macs that have two options. It also allows pinning to the higher or lower power consumption which might be of use. It's not clear if there is no way to get past the OS to exercise control of the CPU or just that no-one has programmed it yet.

Mac OS X has SpeedStep built into the kernel and enabled since OS X 10.4, and, as already has been said, it can no longer be controlled through the System Preferences. There are, though, some applications which will let you configure and set specific clock speeds. All of which I could find, such as CoolBook, do not work on Lion nor support the latest processors.

I could find, though, CPULimit. A script / tool which will let you control the usage of a specific process.

Though Windows and Mac OS X run on x86 platforms , AFAIK, power consumption is handled differently in both the OSes and in Mac OS X it is slightly better. It is better not to use third party tools to manipulate CPU speeds as far as possible. Cheers

In fact , there is GPU power state management in Mac OS X. The kext responsible is AppleGraphicsPowerManagement.kext into Extension Folder.

According to the GPU Core Throttle % ,changes the Power States from 0-4. But I don't know how the kext works for CPU states, this is something I am investigating.