[ltp] T60 battery

[Laurent Gilson]

Hello,

> the CPU has three sleep states C1 to C3,

It has 8 or more speed states but bus master activities prevent it from  
entering states below C3. Removing USB may help, GLX was the breaking  
point for me.

> where C1 uses much more power as C3.

Right. And C8 uses way less power then C3.... and so on.

> if you regulate down the CPU to 1GHz and it needs to come up from C3 to  
> C1 for much longer to finish a task than it would need if it just scaled  
> up for a shorter period of time with automatic scaling enabled you would  
> affectively need more power if you controll it by hand

I donīt think so. I only know the exact values for the PM 725, but i donīt  
think these have changed a lot in the new generation. At 600MHz and full  
load the CPU needs 7.5W typical. At full speed (1600 MHz) and full load it  
is 21W typical (max is 25W). 1600 MHz is 2.6 time faster then 600MHz (if  
the RAM can keep delivering data at 1.6GHz. I donīt think it can, so the  
factor will be a tad worse). 21W is 2.8 times more then 7.5W. Low Speed  
wins.

Put the other way round: 0.013125 W/MHz vs 0.0125 W/MHz. If the calulation  
takes X MHz (and the RAM is lighting fast or everything is in cache) 600  
MHz is the way to go.

Next point: watch out for a undervolting tool/hack for your CPU. I saw a  
project aiming to undervolt Yonahs and i think C2D are also targeted. That  
helps a lot.


For the HD: you can go all the way and install a flashbased HD. I did it  
using squashfs, ramfs and a USB-stick, there are other ways.

Or you can install laptopmode. That will spin down your HD for 10-25 min,  
depending on your usage pattern.

cu