How to properly cool overclocked RPi3?

Cubytus · August 23, 2018 at 12:29 AM

Hi there,

I have a few h265-encoded videos, and of course, the RPi 3 has a hard time playing them. Even though this is not recommended, I overclocked it a bit with the following parameters in /flash/config.txt:

arm_freq=1300

core_freq=500

sdram_freq=500

over_voltage_sdram=4

over_voltage=4

disable_splash=1

#force_turbo=1 #Voids Warranty! (uncomment to avoid CPU scaling down to 600Mhz)

#boot_delay=1 #helps to avoid sdcard corruption when force_turbo is enabled.

#sdram_freq=500 #uncomment to test. Works only with some boards.

For testing purposes, I played one 1080p / hevc encoded movie in a loop, for hours. It didn't crash, but stutters frequently. I read somewhere that the CPU throttled down if the temperature goes above 80. Indeed, the CPU temperature is very high

vcgencmd measure_temp command returns anywhere from 80 to 84.9'C during playback.

The RPi 3 currently sits in the aluminum Flirc Kodi case.

How would I install additional cooling to avoid throttling while playing h265 files?

**Iridium** · August 23, 2018 at 9:43 AM Official Post

1) RPi3B or B+. If B+ are you using the correct thermal pad on the case?

2) Try the latest Milhouse builds as these have improved hevc decoding and should be less CPU intensive - although still not perfect as it still has to be processed in software and not hardware.

3) Your only other real option is to use a fan. I've used 5V mini fans quite successfully which drops the temp by about 10 - 15^obut this won't work with your case. I also found that they tended to be rather noisy but hooking them up to the 3.3v rail dropped it to an acceptable level.

4) N-itrogen (Banned word for some reason) cooling Here or water cooling Here but probably not serious contenders. (Cheaper to buy a AMLogic Box)

Shoog · August 23, 2018 at 11:42 AM

Not on a RSP3, but on a S912 chip, I installed a small heat sink which I salvaged from a south side bus cooler off an old Motherboard. I used loctite threadlock to glue it to the chip. I then used an old salvaged graphics card cooling fan run at 3V3. Runs whisper quiet and keeps my AML S912 down at 50 centigrade. This is enough to keep slow downs at bay.

Shoog

**smp** · August 23, 2018 at 2:14 PM

Quote from Cubytus

vcgencmd measure_temp command returns anywhere from 80 to 84.9'C during playback.

The RPi 3 currently sits in the aluminum Flirc Kodi case.

This shouldn't happen with Flirc case. Looks like there is no contact at all with a SoC and a built-in heat sink.