[Solved] - Tower's 1st [no, 3rd] Hard-Reset since clean-reinstall.

[kdemeoz]

Well I've googled a bit as well for you and found a few possibilities:
1. it can be a power supply issue, your power supply may not be giving the CPUs enough voltage, so it might be that your power supply is near end of life or you have too much peripherals attached for the power supply to handle
2. you motherboard may not be giving the CPU enough voltage, so your motherboard can be near end of life

Thank you. Yes, as i wrote in my earlier post [my Point #5], PSU & MoB were mentioned by various posters per my links, but in my interpretation, these seemed to be Users taking educated guesses rather than categorically proving root cause. As for possibility of either being "near end of life", given my Tower hales from only May 2015, i would be mighty annoyed if true. 

3. since I think you have intel CPU, have you installed a package called intel-microcode? If not, please try it, it will not harm in any way, but enable the system to handle the intel CPUs properly

It is an Intel [Quad core Intel Core i7-4790 (-HT-MCP-) cache: 8192 KB]. Following your advice i have right now installed intel-microcode via Synaptic. 

4. since Ubuntu 16.04, many people have started experiencing the same issue as you, there is an active bug opened with Ubuntu, last post was 22 hours ago - look here: https://bugs.launchpad.net/ubuntu/+sourc...ug/1530405

Um, yes, thanks, i know... that is my 1st link i provided in my earlier post.

5. seems that people with Nvidia cards are having this issue, so even though you have switched to Nouveau driver, maybe I would experiment again with reverting back to proprietary Nvidia driver and checking for the lockups

I did also notice that Nvidia was mentioned many times, but i was confused. Some posters seemed to think that their Nvidia drivers were the root cause [hence they advocated changing to Nouveau], whereas diametrically-opposite some posters seemed to feel it was Nouveau at fault, recommended changing to Nvidia drivers, & actually a few times mentioned they had "blacklisted nouveau" [what does that mean? is it sensible? how to do it?].

I do note your suggestion to try my Nvidia driver again [which i assume you are only making specifically in awareness of my kernel upgrade to 4.9.9, otherwise i cannot see the point, given that the explicit reason i previously switched from Nvidia to Nouveau [per advice from leszek, Pliny & you, if i recall] with the various older kernels was the plethora of freezes]. However, given today's new change already made [the intel-microcode installation, as above], i shall hold off on the GPU driver switch-back until/unless there's another freeze [ie, so i can properly judge the effectiveness or not of intel-microcode].

6. there is a parameter that you can set, that will potentially enable to avoid the lockups - try to set it like this:

Code:

sudo echo 120 > /proc/sys/kernel/watchdog_thresh

By default that parameter is set to 10 seconds. If you prolong it to let's say 120 seconds, it will maybe help. In any case, that behavior is definitely NOT normal and something IS going on there. And in any case, this is DEFINITELY not a Maui thing, I think that you would have similar issues with any other Ubuntu 16.04 derivative. You have to understand that Maui is ONLY the Plasma desktop environment, nothing else - everything else, below that, like graphics, kernels, hardware support etc. is purely related to the Ubuntu and stuff provided by Ubuntu, so whether it's Maui, Neon, Mint or anything else - all is equally impacted. So when you search, please search for stuff related to Ubuntu 16.04.

Golly that's an interesting idea, thanks. I have now done it [which is a bit naughty of me as that's now TWO variables i've changed today, against scientific-method best practice]. Note however that my attempts to do this in Konsole failed:

Code:

Z97-HD3:/$ sudo echo 120 > /proc/sys/kernel/watchdog_thresh
bash: /proc/sys/kernel/watchdog_thresh: Permission denied

So instead i opened the file in Kate as Root & edited its "10" to "120" [should i be worried at Konsole's permission rejection?]. Sigh, that also failed:

Code:

The document could not be saved, as it was not possible to write to /proc/sys/kernel/watchdog_thresh.

Check that you have write access to this file or that enough disk space is available.

There's 125 GB free, so that's not the issue. I'll reboot after posting, & try again.


EDIT: Post-reboot, still "Permission denied". Oh dear, why do these things keep happening to me?