Hello all,

So I have the following issue in Ubuntu 18.10. In games (from Steam such as Cities Skylines, Dota 2), after some time the computer reboots. The reboots usually occur after at least 45 mins of playing or so, but sometimes they occur faster. Sometimes the reboots are persistent (computer reboots, I reenter the game, reboot occurs again shortly after) and sometimes they are not (reboot occurs, I reenter the game and no more issues). They do happen at least once a day though.

Things I tried:
- ran memtest for ~ 2 hours, no issues
- ran mprime (8 threads, tried both type 1 and type 3 tests, for about about ~ 2 hours), no issues
- ran some phoronix test suites (unigine, gui-toolskit), no issues
- ran a phoronix test for the GPU at the same time with mprime, still had no reboot. Maybe it's relevant to mention that test 2 and 3 of the unigpu phoronix test were just white blank screens.
- monitored temperatures while doing the above and both CPU and GPU stayed within temperature limits. CPU never went above 70C and GPU above 76C. When playing Dota (in 4k res) the GPU temp does get very close to 80. Never past 80 though
- upgrading to newer kernel (went from 4.19 to 4.20 via ukuu)
- changing PSU to better new one, did not work
- changing graphics card (from GTX 950 to RX570), did not work

Hardware:
Mobo: ASRock 970M Pro3
CPU: AMD FX-8350
GPU: RX-570 Asus Strix 4G
PSU: Corsair RM-750X
RAM: 16 GB @ 1600 MHz

Software:
OS: Ubuntu 18.10

Some commands and their output:

glxinfo -B 

name of display: :0
display: :0  screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: X.Org (0x1002)
    Device: Radeon RX 570 Series (POLARIS10, DRM 3.27.0, 4.20.0-042000-generic, LLVM 7.0.0) (0x67df)
    Version: 18.2.2
    Accelerated: yes
    Video memory: 4096MB
    Unified memory: no
    Preferred profile: core (0x1)
    Max core profile version: 4.5
    Max compat profile version: 4.4
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.2
Memory info (GL_ATI_meminfo):
    VBO free memory - total: 3336 MB, largest block: 3336 MB
    VBO free aux. memory - total: 3949 MB, largest block: 3949 MB
    Texture free memory - total: 3336 MB, largest block: 3336 MB
    Texture free aux. memory - total: 3949 MB, largest block: 3949 MB
    Renderbuffer free memory - total: 3336 MB, largest block: 3336 MB
    Renderbuffer free aux. memory - total: 3949 MB, largest block: 3949 MB
Memory info (GL_NVX_gpu_memory_info):
    Dedicated video memory: 4096 MB
    Total available memory: 8192 MB
    Currently available dedicated video memory: 3336 MB
OpenGL vendor string: X.Org
OpenGL renderer string: Radeon RX 570 Series (POLARIS10, DRM 3.27.0, 4.20.0-042000-generic, LLVM 7.0.0)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.2.2
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

OpenGL version string: 4.4 (Compatibility Profile) Mesa 18.2.2
OpenGL shading language version string: 4.40
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile

OpenGL ES profile version string: OpenGL ES 3.2 Mesa 18.2.2
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20

lshw -c video output:

  *-display                 
       description: VGA compatible controller
       product: Ellesmere [Radeon RX 470/480/570/570X/580/580X]
       vendor: Advanced Micro Devices, Inc. [AMD/ATI]
       physical id: 0
       bus info: pci@0000:01:00.0
       version: ef
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=amdgpu latency=0
       resources: irq:32 memory:c0000000-cfffffff memory:d0000000-d01fffff ioport:e000(size=256) memory:fea00000-fea3ffff memory:c0000-dffff
I feel I'm running out of suggestions from forums. Anybody have any ideas?

Thanks