You question has delayed very long time but hope you are still using Hikey board. We have enabled thermal management on Hikey with IPA, so when the temperature has increased to over 65'C, it will set constraint for CPU frequency. So it will not trigger reset when you run benchmark.
By default, IPA has been enabled in release. But in some RPB release, it missed to insert kernel module and enable IPA governor for thermal framework, so you need manually enable it by below commands:
test -f /etc/ssh/ssh_host_dsa_key || dpkg-reconfigure openssh-server
echo "power_allocator" > /sys/class/thermal/thermal_zone0/policy
Also please check this linkage for more detailed discussion: