Disconnecting power for MacBookPro reduces CPU speed considerably?

All,

I heard tha when I disconnect the power from my MacBookPro (late 2008), the CPU speed will scale back all the way to 1.5Ghz or something like that. Is that true? If yes, anyway I can configure this?

In WinXP, I can use Intel utility to prevent the SpeedStep...

 

If you need the cpu power it should go back up to normal clock speeds? Unless osx doesnt do throttling, but it should be controlled by the bios anyway

 

I'm not sure to what speed it does throttle down to, but yes if you unplug the power it will underclock the cpu.

You probably wont notice it unless you're running really cpu intensive apps. Everyday use shouldn't suffer that much.

 

Yes, and I believe it can scale it back even when powered by the MagSafe connector. You won't notice any difference as the throttling technology in these processors and the power management in Mac OS X is smart enough to increase the clock speed when required by a resource intensive application.

 

Go it. So it'll pump up the CPU when running something that is intensive. Is there any way to disable this like in Windows world or not?

 

There is no option in OS X to modify the throttling of the CPU, although I have never noticed a drop in performance when in battery mode.

 

The only serious clock limitation is if you take out your battery and power the computer by wall-power only. Then the CPU is clocked at it's lowest clock speed, maybe because of concern that the adapter may not always supply enough power when the system is at max load where usually the battery may help out in short bursts.

For SpeedStep itself on battery power, there is no reason to disable it. It offers virtually no performance improvement since the CPU increases speed to match your performance level anyways, and it only takes a few clock cycles to respond while a 2GHz CPU is doing 2 billion clock cycles per second. OS X is also very good at power management and SpeedStep is a critical part of that. I don't really see a need to lock the CPU at max clock speeds all the time, when it's really not necessary at idle or for surfing the web or even playing a game, because under heavy continuous load the CPU would be ramped to max anyways.

There is a Better Performance power setting. I don't believe it disables SpeedStep, but I presume that the CPU would downclock less aggressively and ramp faster in respond to CPU load.

 

Thanks for the info guys! I'll monitor the performance when running on battery.