Khadas VIM2 Thermal Testing

Gouwa · July 3, 2017, 4:32pm

According the article The First Amlogic S912 Development Board is Coming Soon with Khadas VIM2 on CNX-Software, some users ask me to do a thermal test when full open all CPU cores(Post#15), that’s the reason why I create the topic here

Testing Conditions

Hardware: VIM2 V10 (Pro Model)
Bare board without any housing
Ambient temperature: 32.9 Degree (Shenzhen is quite hot now )
Full open/enable 8 cores
Ubuntu-17.04 with Linux-4.9.26:

root@Khadas:~# uname -a
Linux Khadas 4.9.26 #5 SMP PREEMPT Mon Jul 3 17:47:04 CST 2017 aarch64 aarch64 aarch64 GNU/Linux
root@Khadas:~# cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=17.04
DISTRIB_CODENAME=zesty
DISTRIB_DESCRIPTION="Ubuntu 17.04"
root@Khadas:~#

Test 1: Zero loading

bare board without any housing/case
zero loading

CPUs Freq:

root@Khadas:~# cat /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_cur_freq
100000
100000
100000
100000
100000
100000
100000
100000
root@Khadas:~#

The CPUs freq will keep 1GHz when zero loading

CPU thermal:

root@Khadas:~#  while true; do sleep 1; cat /sys/class/thermal/thermal_zone0/temp ; done
55000
55000
55000
55000
55000
55000
55000
55000
54000
55000
^C
root@Khadas:~#

The CPU thermal is around 55 degree when zero loading

Test 2: Full loading

bare board without any housing/case
Full loading

Enable all CPU cores:

root@Khadas:~# yes "yes > /dev/null&" | head -n8 | bash
root@Khadas:~# top
Tasks: 175 total,   9 running, 166 sleeping,   0 stopped,   0 zombie
%Cpu(s): 23.5 us, 76.5 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem :  2939188 total,  2766972 free,    92236 used,    79980 buff/cache
KiB Swap:        0 total,        0 free,        0 used.  2805492 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND     
 2811 root      20   0    1756    388    320 R 100.0  0.0   0:09.12 yes         
 2814 root      20   0    1756    328    264 R 100.0  0.0   0:09.10 yes         
 2812 root      20   0    1756    360    296 R 100.0  0.0   0:08.98 yes         
 2813 root      20   0    1756    328    264 R 100.0  0.0   0:09.10 yes         
 2815 root      20   0    1756    356    292 R 100.0  0.0   0:09.08 yes         
 2816 root      20   0    1756    352    288 R 100.0  0.0   0:09.04 yes         
 2817 root      20   0    1756    340    276 R 100.0  0.0   0:09.11 yes         
 2818 root      20   0    1756    376    312 R 100.0  0.0   0:08.95 yes         
 2819 root      20   0    6216   2896   2312 R   0.7  0.1   0:00.10 top         
 2059 root      20   0       0      0      0 S   0.3  0.0   0:06.89 kworker/5:1 
 2154 root      20   0       0      0      0 S   0.3  0.0   0:00.46 kworker/4:1

CPUs Freq:

root@Khadas:~# cat /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_cur_freq
1512000
1512000
1512000
1512000
1000000
1000000
1000000
1000000

CPU freq will always keep 1.5GHz@Big-clusters and 1.0GHz@Little-clusters(More than 5 minutes)

CPU Thermal:

root@Khadas:~# while true; do sleep 1; cat /sys/class/thermal/thermal_zone0/temp ; done
75000
74000
75000
75000
75000
75000
75000
76000
76000
76000
76000
76000
76000
76000
76000
76000
77000
77000
77000
77000
77000
77000
77000
77000
77000
77000
77000
77000
78000
77000
77000
78000
78000
78000
78000
78000
78000
78000
78000
78000
79000
79000
78000
79000
79000
78000
79000
79000
79000
79000
79000
79000
79000
79000
79000
79000
80000
80000
80000
80000
79000
79000
80000
80000
80000
80000
80000
...

80000
80000
81000
^C
root@Khadas:~#

The CPU temp will be keep growing from 55 to 80 degree when enable full loading

Test 2.1: Full loading + Heat sink

bare board without any housing/case
Full loading

CPU Thermal:

The CPU temp down 80 to 67 degree when a heak sink is pasted on the top of CPU

But after a while, the CPU temp will start to grow back to 80 degree:

Test 2.2: Full loading + Heat sink + Cooling fan

bare board without any housing/case
Full loading

The CPU temp is going down from 80 to 61 degree when with a heak sink and cooling fan.

Some photos:

theguyuk · July 4, 2017, 10:07am

The right heat sink use and design can make a significant difference. Reading several articles online I suggest can aid better results http://resources.altium.com/altium-blog/maximizing-pcb-cooling-with-best-design-practices-for-surface-mount-heat-sinks

Can I ask what the CPU governor was set to?

geokon · July 5, 2017, 2:51pm

Thanks for the hard work!

Afquintans · August 21, 2017, 9:36am

Hi
In this Vim 2 the “kit Cooling” is the same at Vim normal?

Best regards

Gouwa · August 21, 2017, 4:57pm

Yes, can work on GPIO, but not recommended as there is an onboard 0.8mm pitch fan header on VIM2

Afquintans · August 22, 2017, 8:15am

Thanks Gouwa
In the Gearbest VIM 2, tester talk about the coolling fan and the Gearbest does not have (https://youtu.be/FZX6c8o5kzo).
Is it planned to receive the product in a Gearbest? It seems important to have already that it is essential a box to take this article to work in full as it happens in the normal Vim

Txemoto · September 9, 2017, 5:07pm

As with the VIM, a heatsink is a must have in this device. Why don`t you put it with the device in the initial design?