[Samsung Infuse 4G] electricpete1:
more test results

I have completed some testing using PowerTutor and results reported in attached spreadsheet.

I would say the results only muddy things further. Don’t read any further if you don’t have a tolerance for ambiguity.

SETUP (common to all tests)

In all tests, I had similar setup as in the original post: 1 channel of “relax and sleep” running to create a constant cpu load, and all other continuous-run programs turned off except power tutor.

Some other details common to all tests: Tasker off, Wifi off, data off, Power Tutor on

No uv

Noop I/o governor used throughout.

WHAT CHANGES BETWEEN TESTS:

See the spreadsheet, tab labeled “summary”.

The things that changed between tests are in rows 3 thru 8, labeled “Tested Configuration”

As you can see, between tests, I varied the Up threshhold and Down threshhold. I varied the kernel. I varied the governor (mostly conservative, but performance used).

WHAT WAS RECORDED DURING EACH TEST:

1 – Recorded power usage of CPU, LCD, Audio as reported in Power Tutor over the course of one minute. I converted them to battery %/hr (conversions shown in tab “Notes”) and listed them in rows 12-14

2 – Recorded the actual cpu frequencies seen in setcpu “home” screen, similar to original post and listed these in row 15. I attempted to guess the average frequency over time and put this in row 16.

3 Rows 18-23 are the Quadrant results for the six categories that Quadrant reports (yes, I know people don’t like Quadrant, just recorded as a datapoint)

WHAT PATTERNs EMERGE:

1 – Entropy’s DD and Zen’s Infusion-A use comparable power (as reported by Power Tutor) in this particular experiment.

2 – Zen’s Infusion does better on quadrant score in this particular experiment, when both are set at the same governor configuration (100-1200, conservative), . Not surprising since Zen said he has optimized for performance.

3 – How does the governor frequency affect power usage? This is the muddy part. There is no doubt that if we blindly take the data at face value, then there IS a correlation between cpu frequency and power attributed to the cpu by Power Tutor. However the correlation that emerges from the data is in the opposite direction from what anyone in the world would think: this data suggests that increasing CPU frequency causes decrease in power consumption reported by power tutor. See tab labeled “chart 1” for graphical depiction of this result.

As you can see in the graph, there is not a random spread of results (as would be the case if random unacconted-for errors were at work). There is a definite correlation. What it suggests perhaps is that there can be a systematic error in the way PowerTutor measures power that depends on cpu frequency.... in other words the error itself (between measured and actual) somehow depends on cpu frequency.

So, I am just reporting some results. I am definitely not suggesting anyone overclock to save power (that would be truly bizarre and I’d probably be kicked out of xda for suggesting something so silly).

On the other hand, as stated in the 2nd post of this thread, I’m still very leery of using cpu frequency as an indicator of power that cpu is drawing... because there is just too much going on inside that black box that I don’t know about. For one thing, the cpu itself may draw different amounts of power at a given frequency depending on it’s loading because the registers may not be doing anything at low loads. For another thing, there are a lot of other things in the phone (like RAM, bus) that may draw some power but probably get lumped in with the reported cpu power in Power Tutor and others. Perhaps the cpu is somehow more efficient at interfacing with these others parts of the system when cpu is at high speed, enabling it to reduce the power they draw. The point is, it’s a lot more complicated then I assumed in my first post.