[tech] Cobra intermittent/slow graphics issues

[James Arcus]

Hi all,

Myself, [DAS] and [MVP] removed Cobra and worked on diagnosing a few issues
with "intermittent crashes" and "slow graphics". We found 3 separate
issues, two of which have been resolved and one that appears to be
identified and needs further attention.

Unfortunately, it seems the main GPU slot on the motherboard is loose in
some way, which allows intermittent issues to crop up. I'm not sure if
there is some way to brace the card to prevent vibration/jolts from
impacting the connection, but otherwise I assume the fix will require a new
motherboard.

Issue:

   - Windows Boot Manager had disappeared from GRUB boot menu

Resolution:

   - Boot to Linux, ensure that the Windows disk is recognised, then run
   `sudo update-grub`
   - Option has returned to boot menu

Issue:

   - Slow graphics/lagging in GPU-accelerated programs

Resolution:

   - DVI connector for monitor was connected to onboard graphics
   - Move DVI connector to dedicated graphics card and reboot
   - GTX 960 is autodetected on boot and applications behave correctly

Issue:

   - Intermittent graphics freezes/crashes

Resolution:

   - Issue not initially observed when running on dedicated graphics after
   above fix
   - Issue was observed after [MPT] bumped the card whilst the side panel
   was open and card was not screwed to backplate
   - Graphics freeze followed by reboot could be reliably recreated by
   pushing slightly up or in on the card even when secured
   - No obvious resolution, other than isolating Cobra from vibrations and
   jolts
   - Issue not observed to occur when machine/table is left alone

Thanks to [DAS] and [MVP] for the help.

Cheers,

James [MPT]
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