Power & Source of Big Ideas

Power requirements

Moderators: chensy, FATechsupport

Hi all,

I've just tried to run some projects on BOINC with my M3 on 5V-2A power (AC-USB plug) but then the screen blacks out upon CPU ramping up to 100%, comes back but system has hanged. I can only restart by holding the power button on the board. On the specs list, the board is listed as taking 5V-2A power but on another page, it is 5V-3A.

So is this a case of insufficient power provided for 100% CPU load? Thanks.
If the USB cable quality is not good enough, will lose power, you can try to use the gpio pin to power M3
I can try with other cables. But the main issue is if 2A is enough to power the M3 at full load?
cowboy36289 wrote:
I can try with other cables. But the main issue is if 2A is enough to power the M3 at full load?


Forget about Micro USB for anything needing more than a few mA. This stupid connector is rated for 1.8A max (not enough for running heavy stuff on all 8 CPU cores) and most if not all USB cables are crappy (leading to high voltage drops since cable resistance is way too high and adds to contact resistance of the crappy Micro USB jack).

You have to use the 4 pin header to provide power and you need a stable PSU able to provide more than 2A without voltage drops. I tried running an optimized Linpack benchmark on this board but had to limit max cpufreq ro 1300 MHz since at 1400 I had a brownout every time.

Not specific to M3 but worth a read: http://linux-sunxi.org/Powering_the_boa ... connectors
tkaiser wrote:
Forget about Micro USB for anything needing more than a few mA. This stupid connector is rated for 1.8A max.


So even a 3A wall plug to micro-USB will not provide the system with enough juice for full load?
cowboy36289 wrote:
So even a 3A wall plug to micro-USB will not provide the system with enough juice for full load


How should this work? Micro USB is crap for powering devices that need juice. It's rated for 1.8A max (9W) and when there's heavy stuff running on all 8 CPU cores consumption exceeds this limitation while the 'average' USB cable already leads to such a high voltage drop that your board already powered off.

Please read the last paragraph here: https://www.loverpi.com/blogs/news/9353 ... comparison

Unfortunately the RPi foundation started with this mess over 4 years ago and since then other vendors also followed. Every engineer out there knows that Micro USB is not suitable for this purpose (due to the fact that most USB cables around have a resistance way too high) but marketing people seem to be able to overrule this.
I tried it out at full load again (all 8 cores running Enigma@Home - BOINC) with the cable which came with my newer phone which supports QC 1.0 (up to 2A charge rate). With the cheapo 5.1V/2.1A adapter, system restarted itself after just 3 minutes. With the adapter which comes with my QC 1.0-capable phone, it's still running strong after 30 minutes, maxing out at 83-86 deg C.

Now it's just for me to find out if it's able to sustain itself indefinitely since the thermals seems fine to me, compared to my other Odroid XU4, running full load and maxing out at 95 deg C (the throttle threshold). Waiting for my 3A wall wart to arrive in a few weeks.

EDIT: T+12hrs still running strong, thermals stable

P.S. Does anyone know the temperature limit whereby the M3 will start to throttle down?
cowboy36289 wrote:
P.S. Does anyone know the temperature limit whereby the M3 will start to throttle down?


85°C: https://forum.armbian.com/index.php/top ... entry13803

:D No wonder it kept steady around that temperature. Seems to throttle down for a short moment to 700/800MHz then goes back up to 1.4GHz. Is there anyway to change the throttle threshold?
cowboy36289 wrote:

:D No wonder it kept steady around that temperature. Seems to throttle down for a short moment to 700/800MHz then goes back up to 1.4GHz. Is there anyway to change the throttle threshold?


The throttling strategy should be better changed since as soon as throttling starts performance drops way more than necessary. When I did some benchmarking back then I had more success manually controlling behaviour (eg. limiting cpufreq by fiddling around with sysfs nodes) than letting throttling jump in.

This is kernel stuff the vendor should be able to answer but since they do not answer to more simple questions (eg. powering of LCD backlight) I've not that much hope that they're able to help. In other words: improving heat dissipation is the only option.
cowboy36289 wrote:
Is there anyway to change the throttle threshold?


By installing cpufrequtils you can at least increase performance by defining the upper cpufreq treshold in a sane way. Since throttling always clocks down to the lowest value possible (800 MHz) adjusting the upper value in a way so that no throttling occurs later is the better idea if you run continuous heavy loads. Or you improve heat dissipation (large heatsink + large fan can be almost silent)
tkaiser wrote:
adjusting the upper value in a way so that no throttling occurs later is the better idea if you run continuous heavy loads. Or you improve heat dissipation (large heatsink + large fan can be almost silent)

I suppose you meant setting the freq ceiling lower so I can run it at 100% with lesser opportunity for system to reach the temp and throttle? I guess I can give it a shot since I have a space constraint on having a larger HSF than the one mounted onto the board now.
I will try to call others, but the main problem is if it is sufficient to 2A M3 power at full load?
sukk741 wrote:
I will try to call others, but the main problem is if it is sufficient to 2A M3 power at full load?

With proper adapter and cable, it sure can as in my case.
cowboy36289 wrote:
sukk741 wrote:
I will try to call others, but the main problem is if it is sufficient to 2A M3 power at full load?

With proper adapter and cable, it sure can as in my case.


Did you ever try to run cpuburn-a53 on your device? https://github.com/ssvb/cpuburn-arm

BTW: Very nice read why Micro USB to power a board is always a crappy idea: https://forum.mqmaker.com/t/miqi-based- ... ning/605/9
Hi guys,
If your M3 connect a fan and LCD or HDMI, we suggest you use a 5V/3A power . Such as the photo

Image

thank you!
cowboy36289 wrote:
I can try with other cables. But the main issue is if 2A is enough to power the M3 at full load?


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You need to use a good quality power supply. The many cheap ones may say 5V 2A but rarely output much more than 1 amp before the voltage drops.

Meanwell do some very good power supplies that work well with the FA boards.

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