This my experience as well from running an X1400 on a Thinkpad and various distros. Clocking down fglrx has always given me much better battery life than using the defaults in radeon and the laptop is certainly cooler as well.
Originally Posted by Melcar
What relevant and working radeon options are actually possible to specify in xorg.conf to get better battery life? The docs are not really clear on this.
The results were directly ready by the Phoronix Test Suite off of the exposed ACPI sensors on the laptop.
Originally Posted by Louise
Okay, this means that if you do the measurement again on another laptop you will of course get other results.
Originally Posted by Michael
As you know, components in laptops are the cheapest components they can get away with in order to lower cost.
The best you can do is to open the laptop and find the components that actually do the measurement and look in their data sheets.
Or try and ask on a electronics newsgroup how accurate they would guess such components in laptops are.
I wouldn't be surprised if each measurement have a +/- 10% accuracy.
I guess there are two kinds of accuracy that need to be considered.
One is absolute accuracy; if the test says 19 watts then what is the likely range of "true" values ?
One is the relative accuracy; if you measure *exactly* the same thing 10 times in a row what distribution of results do you get ? Put differently, if you *compare* two sets of measurements with the same equipment how valid is the comparison ?
For an article like this (where the goal is to establish differential readings for the same system and same tools with different drivers) the second form of accuracy is probably more relevent, ie absolute accuracy (calibration etc..) doesn't matter as long as two sets of measurements closely related in time give similar results.
Louise, does that make sense ? If so, what information would you use to determine the size of the error bars ?
Last edited by bridgman; 03-06-2009 at 09:45 PM.
It is only in discrete cases (things you can count) where is it possible to do exact measurements. E.g. how many cars passed a censor in an hour.
Originally Posted by bridgman
I don't understand why you would go with relative accuracy (distribution) for this test.
Distribution is used when you want to predict values you haven't measured.
Btw. The plots really need horizontal tick marks and unit, so the number of measurements can be seen.
This is something I've been meaning to ask for a while... does DynamicClocks actually do anything on my 9250? For that matter, does even manual clock adjustment have any effect on power draw?
Pretty futile to try considering the GPU's power consumption is nothing compared to my P4, but I was curious.
I've manually underclocked my R500 and R700 but the effect of clock speed was minimal. Underclocking the card's memory might give you a watt or two, but don't expect miracles. However, underclocking allows you to reduce the GPU voltage, which has a positive impact in power consumption (and noise!)
Personally, I've updated the BIOSes of both cards with custom voltage and clock tables. This works rather well, although YMMV.
Now, if only R700 wasn't so trigger happy... Scrolling a window or watching a (SD) video shouldn't launch the high-performance profile. Even underclocked, this card has more than enough juice for day to day use, no need to put the memory to 2GHz every time I move my mouse dammit!