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Author: bronco

Operating the H3 in a reliable way (sane clockspeeds)

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 Author| Post time 2015-12-4 16:31:46 | Show all posts
hojnikb replied at 2015-12-4 16:07
Is it possible to go lower with the voltage ?
Something like 800mV for 240Mhz.

Maybe this works. But it's already below the recommended minimum according to the user manual. And it doesn't help that much with further savings.

The other end of the scale is more interesting since a slight increase in voltage leads to massively more consumption/heat. I can't explain it well since I'm an electrics NOOB so better read from here on: https://olimex.wordpress.com/201 ... -way/#comment-20385

And this is exactly the reason the Orange Pi Plus/2/PC users suffer from heat problems: Since the dvfs settings used with every OS image are broken: Only 2 voltages defined, the upper beyond specifications (1.5V) and the lower also on the upper limit (1.3V). By simply adjusting these to sane values und using a few more dvfs table entries all the problems are gone.

And for my use cases the H3's 4 cores are great since you can operate the SoC at low clockspeeds (then also low voltages) what really helps lowering consumption/heat. This is where the H3 can really shine: http://www.orangepi.org/orangepi ... 6&fromuid=29411

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Post time 2015-12-5 00:27:41 | Show all posts
I suppose recommended minimums are meant for stable operation for even the crappiest quality bins.

But the bigger question is whenever it actually sets 800mV if you define it in the dvfs table or just ignores it and sets the recommended minimum.

Defenetly needs testing.
 Author| Post time 2015-12-6 02:46:19 | Show all posts
hojnikb replied at 2015-12-5 00:27
I suppose recommended minimums are meant for stable operation for even the crappiest quality bins.

...

You might run into stability problems. And the potential savings aren't worth the efforts.

It makes nearly no difference regarding consumption/temperature when you decrease voltage from 900mV to 800mV but it's a completely different story at the upper limit of the scale: 1400mV vs. 1500mV make a huge difference. By simply stopping this overvolting most of the heat/stability problems (and the need for a fan) are gone.
 Author| Post time 2015-12-7 07:02:33 | Show all posts
A few final words: http://linux-sunxi.org/User_talk ... e_Frequency_Scaling

I let the test script also walk through my 'headless' settings with further reduced voltage (on the right):



It's not worth the efforts to undervolt further. The most important change is to escape from Xunlong's overvolted dvfs table with only 2 entries leading to all sorts of heat/stability problems the forum is full of.

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Post time 2015-12-8 00:23:58 | Show all posts
Thank you for your work. Stability is my main concern so I will definitely follow your advice.

OPi PC will be working in my beer cellar, any additional heat dissipation is not welcome.
 Author| Post time 2015-12-8 01:03:19 | Show all posts
Edited by bronco at 2015-12-8 01:20
zgoda replied at 2015-12-8 00:23
OPi PC will be working in my beer cellar, any additional heat dissipation is not welcome.

Today my 2nd OPi PC arrived and I had the chance to try again without a heatsink: It's crazy how these moronic dvfs table settings then look. On the left the 'defaults' with only 1.3V for all lower cpufreqs and 1.5V above 1.2 GHz defined. On the right sane settings:


Results without a heatsink, no enclosure (!) and upright position (helps a little bit due to convection):

Xunlong settings:
Idle at 480MHz/1300mV: 1.7 W consumption and 48°C
Idle at 1536MHz/1500mV: 2.1 W consumption and 60°C

Sane settings:
Idle at 480MHz/980mV: 1.5W consumption and 43°C
Idle at 1200MHz/1240mV: 1.6W consumption and 47°C


Given you combine the wrong dvfs settings (Xunlong's) with the performance governor you end up with a device that doesn't idle at 43°C but at 17°C more. While consuming a whopping 0.6W more. Still DOING NOTHING. That's the price you pay for accepting these weird overvolted/overclocked settings. It's obvious based on the graphs where the heat problem originates: Overvolting.

And given you put your H3 device into a small enclosure it might be easily possible that idle temperature exceed 70°C or even more. Still while being completely idle

At the moment I let the test script walk through my undervolted settings (not recommended since they're not expected to work with a connected display) and then I repeat the whole series of tests also firing up cpuburn-a7 to get an idea how fast throttling occurs without heatsink with Xunlong's insane default vs. sane settings...


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Post time 2015-12-8 02:25:44 | Show all posts
Will you share the script for others to test ?