undervolters:

does cpu load affect how much power the CPU is drawing / heat generated?

 

In one word: YES.

If you are doing some light work (internet, office applications..) than your laptop will remain fairly cool, and CPU will automatically throttle down it's FSB, thus low heat is generated. (Such as Turions featuring Cool N' Quiet). If you play games for 1-2 hours straight, then your laptop will get warm/hot.

 

even if i've manually locked it into 800mhz mode?

 

Hi hegemon,

locking it at 800MHz doesn't actually mean that you affected the LOAD! I mean some medium task on highest freq will be using more CPU power (higher load) on locked 800, but that is not an issue. You locked the frequency at which you can still have 0-100% load. 100% load on 800 MHz produces more heat than 0% load (idle) on higher frequencies.

Locking freq of 800MHz will in the end be cooler than higher frequencies just because of voltage at different multipliers (freqs) and the fact that CPU spends a lot of time on idle, so even if you use it 100% it will quickly cool off once it is on idle.

Cheers,

 

Higher the load the higher the heat. But the highest typical temp you get at 800mhz won't be near what you would be getting if you had it unthrottled at max load.

 

Running at lower speed for the same task means longer running time. It is hard to estimate the total heat generated per task, but at a lower speed, the heat sink and cooling fan may be more efficient to cool it down even at a longer run.

 

so if i'm doing a task that has a constant 30% load at 800MHz (PowerDVD) is that going to use more or less power than running the same task at a higher clock speed?

 

if the task requires only 30% of 800mhz, then certainly you will be using less power. If you disable the throttle the CPU would use 1.5v (35w) and do the task for the same time period. By undervolting you give the processor only 0.925v (?w) without sacrificing performance

 

Ofcourse yes.

Power consumption is depends on Clock Speed , Voltage and load.

Even if you are giving same voltage at 800Mhz and 1600Mhz, it still consumes more power at 1600Mhz.

So, effectively, there are two way power consumption is affected.

1. CPU Clock speed x voltage
2. CPU load

So, typically using CPU at 50% at 800Mhz consumes less power than using CPU at 25% load( I mean same load) at 1600Mhz. So sticking to lowest possible freq is the way to reduce heat and power.

 

ok, thanks guys. And Chinna, definately right about dvd playback. PowerDVD is the way to go. the included WinDVD wanted 70% @ 800MHz