I was able to pkg_add stress without a crash and set up a script. Running for about 1 minute at 816Mhz did not have problems. Usually a pkg_add of much shorter duration at this speed will result in a crash. I ran a 10 sec test at 1300Mhz successfully, but the cpu got very hot, > 60 degC. I should put on a heat sink. I think the dwxe driver needs to be looked at. Networking often stops working without a system crash and any system crash I have seen has always involved networking.
Stress test: oppc2opbsd# ./test.ksh hw.machine=arm64 hw.model=ARM Cortex-A53 r0p4 hw.ncpu=4 hw.byteorder=1234 hw.pagesize=4096 hw.disknames=sd0:1e111df47ad2925f hw.diskcount=1 hw.sensors.sxitemp0.temp0=35.77 degC (CPU) hw.sensors.sxitemp0.temp1=36.61 degC (GPU) hw.cpuspeed=816 hw.setperf=60 hw.product=Xunlong Orange Pi PC 2 hw.physmem=944402432 hw.usermem=944390144 hw.ncpufound=4 hw.allowpowerdown=1 hw.perfpolicy=manual hw.ncpuonline=4 Sat Feb 2 16:52:15 PST 2019 hw.sensors.sxitemp0.temp0=35.77 degC (CPU) Sat Feb 2 16:52:20 PST 2019 hw.sensors.sxitemp0.temp0=43.52 degC (CPU) Sat Feb 2 16:52:25 PST 2019 hw.sensors.sxitemp0.temp0=45.78 degC (CPU) Sat Feb 2 16:52:31 PST 2019 hw.sensors.sxitemp0.temp0=47.57 degC (CPU) Sat Feb 2 16:52:36 PST 2019 hw.sensors.sxitemp0.temp0=47.21 degC (CPU) Sat Feb 2 16:52:41 PST 2019 hw.sensors.sxitemp0.temp0=47.57 degC (CPU) Sat Feb 2 16:52:46 PST 2019 hw.sensors.sxitemp0.temp0=48.88 degC (CPU) Sat Feb 2 16:52:51 PST 2019 hw.sensors.sxitemp0.temp0=48.28 degC (CPU) Sat Feb 2 16:52:56 PST 2019 hw.sensors.sxitemp0.temp0=49.11 degC (CPU) Sat Feb 2 16:53:01 PST 2019 hw.sensors.sxitemp0.temp0=49.23 degC (CPU) Sat Feb 2 16:53:06 PST 2019 hw.sensors.sxitemp0.temp0=49.35 degC (CPU) Sat Feb 2 16:53:11 PST 2019 hw.sensors.sxitemp0.temp0=41.02 degC (CPU) stress: info: [11364] dispatching hogs: 2 cpu, 1 io, 1 vm, 0 hdd stress: dbug: [11364] using backoff sleep of 12000us stress: dbug: [11364] setting timeout to 60s stress: dbug: [11364] --> hogcpu worker 2 [46487] forked stress: dbug: [11364] --> hogio worker 1 [40186] forked stress: dbug: [11364] --> hogvm worker 1 [5677] forked stress: dbug: [11364] using backoff sleep of 3000us stress: dbug: [11364] setting timeout to 60s stress: dbug: [11364] --> hogcpu worker 1 [62526] forked stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [5677] freed 536870912 bytes stress: dbug: [5677] allocating 536870912 bytes ... stress: dbug: [5677] touching bytes in strides of 4096 bytes ... stress: dbug: [11364] <-- worker 46487 signalled normally stress: dbug: [11364] <-- worker 40186 signalled normally stress: dbug: [11364] <-- worker 62526 signalled normally stress: dbug: [11364] <-- worker 5677 signalled normally stress: info: [11364] successful run completed in 49s