fit-IoT Users Forum

Prior to beginning work on a Fitlet Power Over Ethernet Project, I needed to know Fitlet's input current and power requirements. I was looking for maximum levels, so I loaded the system to 100% by simultaneously streaming a video and generating a complex fractal image. The only connected power consuming peripheral was a set of USB powered speakers.

Here are the results of the test.

System: Fitlet i-A10 with internal SSD
OS: Linux Mint v17.1 Rebecca
Applications: Mandelbulber Fractal Generator & Streaming Video
System Load: 4 Cores Loaded to 100%, GPU, wifi module, and USB powered speakers


For BIOS TDP Setting = 4.5 Watts



For BIOS TDP Setting = 10 Watts
The tests show I should have no problem powering Fitlet via POE+, even for higher TDP settings and high system loads.

Thanks for sharing your power consumption analysis data on fitlet-iA10. It can be a good reference point for many fitlet users.

Interesting. What did you boot from?

Hi hassellbear,

Thanks for your response in my other thread. Your measurements are great. I am however stumped by the low power consumption you get at full CPU load.

Your measurements at full CPU load show:
4.5W TDP ==> 6.5 Watts Consumed
10W TDP ==> 8.7 Watts Consumed

My numbers are quite different. I disconnected everything from the PC. I remained connected over WiFi, though it wasn't in use. I stressed the CPU with Prime95 Torture Test.

My measurements in Windows at idle:
4.5W TDP ==> 5.7 Watts Consumed
10W TDP ==> 6.1 Watts Consumed

My measurements at full CPU load with low RAM usage:
4.5W TDP ==> 10.7 Watts Consumed
10W TDP ==> 11.1 Watts Consumed

My measurements at full CPU load with high RAM usage:
4.5W TDP ==> 11.8 Watts Consumed
10W TDP ==> 12.5 Watts Consumed

This shows that moving from idle to full CPU load adds about 5 Watts for the 4.5W TDP condition and 6 Watts for the 10W TDP condition. Do you see a similar jump when going from idle to full CPU load?

You're results also show a much larger difference in power consumption for 4.5W and 10W TDP settings (~2W vs my ~.5W).

What do you think?

Thanks!

Hi IntensePC_User,

Hmmm - this deserves a bit of attention. My thoughts are:

1. My graphical power levels were obtained by logging current and multiplying those values by an assumed 12 VDC. In actuality, the supply voltage runs closer to 13.9 VDC, so my graphical power values are probably around 86% of the actual values. Making the necessary corrections closes the gap somewhat, but my adjusted values are still lower than yours.

In later tests, I used an actual DC power meter. I should probably recreate the graphical tests using that meter.


2. In a later test, the DC power meter showed an idle power level of 4.1 watts for a TDP setting of 4.5 watts. This is 1.6 watts below the idle power you measured.

See : http://www.fit-pc.com/forum/viewtopic.php?f=149&t=5670

I suppose it is possible my wattmeter reading is inaccurate because the current is on the low end of its measurement range. A bit of validation is in order here.


3. The method I am using to load the processor results in the Linux System Monitor reporting a sustained load of 100% for all 4 cores. However, my method may not be loading the system to the level of your "true" stress testing application.

4. Is it possible the CPU frequency scaling governors behave differently in Linux and Windows? Could this explain some of the difference in the idle power levels?


I think I will verify the accuracy of my wattmeter and recreate the graphical tests if it proves to be accurate on the low end of its current range. This time I will use a true stress testing application.


Best regards - hassellbear

I think you may be on to something with CPU scaling at idle. Watching the CPU frequency (as a % of maximum), it rarely falls below 80 or 90% with no activity. Maybe Linux is more aggressively scaling like you suggest.

However, loading my CPU fully fuels a power consumption jump just above that of the default TDP (4.5W).

The DC power meter i'm using supposedly works down to 1mW with 1mW precision. I've seen some other posts on here that point to 5.5W at idle.

What i'd love to do is fully disable the graphics chip to run headless, but so far i haven't found a way to do that in the BIOS.

Thanks for your input!