Why is Expose jerky when using my MBP with a battery instead of power supply?

[Neutral Gamer]

I've got a 17" Macbook Pro with Hi-Res screen and 160GB 7200rpm HDD.

When it's plugged in all animations for Expose, Dashboard and even Desktop Manager (excellent program until Spaces arrives!) are super smooth every time. But when I use it without the power supply the animations become jerky - only if you repeat the animation straight away does it then become smooth.

I assumed it was something to do with the Energy Saver profile but I've tried them all, including Better Performance and my own Custom one yet none of them make any difference.

Does something happen internally to increase battery power when not using the power supply, i.e. is the processor / graphics card not being used at full speed until it's required or something?

Also, what exactly does Better Performance do compared to Normal? Does it even make a difference when you're using the power supply?

I really enjoy using such a powerful laptop - it's much faster than my current PC desktop. It's just a pity that I seem to get less impressive performance when using the battery only, i.e. when using it as an actual mobile laptop rather than a portable, plugged in desktop.

Any help would be grateful!
Cheers

 

[flopticalcube]

The GPU might be clocked down on battery to save energy.

 

[Eidorian]

The video card can be clocked down while on battery power. I know mine does in Windows.

 

[Neutral Gamer]

Wow, thanks for the super quick replies!

Any way of keeping the graphics card locked in at a particular clock rate, i.e. 3rd party apps?

 

[Eidorian]

Wow, thanks for the super quick replies!

Any way of keeping the graphics card locked in at a particular clock rate, i.e. 3rd party apps?

It should clock up for games and 3D intensive applications but I'm unsure how it's handled on battery power.

 

[MacinDoc]

Wow, thanks for the super quick replies!

Any way of keeping the graphics card locked in at a particular clock rate, i.e. 3rd party apps?

Go into System Preferences>Energy Saver. Choose Battery Settings and set to Maximum Performance.

Unfortunately, this can't be application specific, and applies to all functions.

 

[Neutral Gamer]

Go into System Preferences>Energy Saver. Choose Battery Settings and set to Maximum Performance.

I can't find a "Maximum Performance" option only "Better Performance". But it doesn't makes any difference I'm afraid.

I've currently got Mail and iPhoto both zoomed in to fill the desktop and Safari zoomed in to fit this web page. When doing Expose all windows, it's definitely smoother with the power supply plugged in. Literally take out plug, Expose jerkiness sets in no matter how many times I repeat the animation.

 

[runplaysleeprun]

The difference between better performance and Normal is that the system in "Normal" will determine the CPU speed automatically, increasing it to maximum when needed, and slowing it when the computer isn't doing anything intensive. In better performance, it is always at its Maximum, even when not doing anything.