Zero 3W running hot

[langweiler]

I have noticed a tendency for the Radxa Zero 3W to run hot even under moderate load. This seems to be true for the CPU itself, but also the black chip next to it (RAM?).

I am running the Zero 3W with the Debian Bullseye image. According to cpufreq-info, the kernel already uses the “ondemand” governor.

$ cpufreq-info
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Bitte melden Sie Fehler an cpufreq@vger.kernel.org.
analysiere CPU 0:
  Treiber: cpufreq-dt
  Folgende CPUs laufen mit der gleichen Hardware-Taktfrequenz: 0 1 2 3
  Die Taktfrequenz folgender CPUs werden per Software koordiniert: 0 1 2 3
  Maximale Dauer eines Taktfrequenzwechsels: 149 us.
  Hardwarebedingte Grenzen der Taktfrequenz: 408 MHz - 1.42 GHz
  mögliche Taktfrequenzen: 408 MHz, 600 MHz, 816 MHz, 1.10 GHz, 1.42 GHz
  mögliche Regler: ondemand, performance, schedutil
  momentane Taktik: die Frequenz soll innerhalb 408 MHz und 1.42 GHz.
                    liegen. Der Regler "ondemand" kann frei entscheiden,
                    welche Taktfrequenz innerhalb dieser Grenze verwendet wird.
  momentane Taktfrequenz ist 1.42 GHz.
  Statistik:408 MHz:6.38%, 600 MHz:10.76%, 816 MHz:0.00%, 1.10 GHz:0.24%, 1.42 GHz:82.62%  (42667)
analysiere CPU 1:

So, I guess this is by design and the only thing I can do is use a better heat sink? Or is there anything else I could do?

At the moment, I am using the standard heat sink sold by Alltech.

For my application, I need the hole setup to be flat and I cannot have active cooling.
Doing some research I came across this solution for the Raspberry Pi Zero, which may also work for the Zero 3W.

Anyone able to share some experience in this regard?

[avaf]

The board rendering video from the camera can reach 85ºC on my experiments.
I finally got a working u-boot with my kernel (and wifi) and soon can test some optimizations with ubuntu and see what i get.

I think HDMI output is to blame… Have you tried disabling HDMI?

[langweiler]

No I have not. That would be somewhat counter-productive since I am using the Zero 3W for a digital photo frame application. I am afraid HDMI output is required. However, I could live with low performance settings since the photos are fairly static.

When I said hot before, I meant I burn my fingers if I touch the heat sink for more than 2 seconds. In the meantime, I have found sensor readings in the sys file system. This is what I get after indexing a few thousand photos:

Zone 0: 72.8 °C
Zone 1: 71.1 °C

Not extreme, but from my experience rather high. I am more used to temperatures around 60 °C with other SBCs.

[avaf]

root@radxa-zero3:/home/rock# cat /sys/devices/virtual/thermal/thermal_zone0/hwmon0/name
soc_thermal
root@radxa-zero3:/home/rock# cat /sys/devices/virtual/thermal/thermal_zone1/hwmon1/name
gpu_thermal

[avaf]

Have you tested that heatsink ?

I ordered one of this to see it it fits:

[langweiler]

I finally found some time to install the Waveshare Zero-HEATSINK, which I mentioned in my previous post.

I used the included red heat conducting pad (1.5 mm, probably 14.5 W/mK, not specified) for the Rockchip CPU. It is slightly smaller than the chip, but sufficiently covers the area contacted by the heat sink.

For the RAM chip I used blue heat conducting pad (1.5 mm, 6 W/mK), which I had to buy separately. In fact, I stacked 1 mm and 0.5 mm pads since I did not have the required 1.5 mm at hand.

The screws shipped with the heat sink did not work for me. The distance between the heat sink and the board was too large and would have required 2 mm or even thicker pads, which is evidently bad for the heat transfer.

I thus used M2.5 plastic hex spacers with sufficiently long screws and two hex nuts per spacer, which I still had at hand from another project (left side). Spacers, hex nuts and screws shipped with the heat sink are shown on the right side for comparison.

Overall the heat sink fits well albeit it literally sits on the USB ports.

Now the result after 30 min uptime running idle at approx. 21 °C room temperature:

SOC: 44.4 °C
GPU: 43.8 °C

Not bad I would say compared to the >70 °C, which I measured before. I definitely do not burn my fingers any longer when touching the heat sink. And the risk of thermal throttling should be significantly reduced.

@radxa How about selling this or a similar heat sink with the properly sized heat conducting pads and screws as an accessory for the Radxa Zero 3W? One anyway needs a heat sink to run this board. It would mean less trouble for your users and additional business for you.

[RadxaYuntian]

I remember @Alvin was using a stick on heatsink on ZERO 3 and it worked OK for him.