Freezing with dual-monitor setup

[fox]

Following up on Jason's suggestion, I did a memory check, albeit a short one, and came up with no memory problems. Then I decided to do something that wasn't on my list - I reinstalled Ubuntu 16.04 from scratch, not copying any old config files to the new partition. The old 16.04 is still there, but I have been working with the new one yesterday and today, and slowly introducing non-vital applications. No freezing yet, so I'm cautiously optimistic. Here is what's different between the old and new:
(1) On a different part of the SSD, since I shrunk the old partition to make room for the new.
(2) I am running only Unity; I have not installed Gnome yet.
(3) I did a few system updates (on both partitions).
(4) I am still running the default video configuration: nouveau driver and "reversed position of monitors" (I have to move cursor to the right of my screen to get to the monitor to the left of the internal one.

Here is the sequence of actions I propose to try to see what causes the freezing, if in fact the new installation itself didn't solve the problem:
(1) change the monitor configuration to make the relative position correct;
(2) install the nvidia driver;
(3) install the Gnome desktop;
(4) remove the old partition entirely
Feel free to comment or suggest another plan of action - I want this problem solved!!!! 

[buster]

(4) I am still running the default video configuration: nouveau driver and "reversed position of monitors" (I have to move cursor to the right of my screen to get to the monitor to the left of the internal one.

Not sure what this means. If you rearranged your desk and physically reversed the position of the monitors, would that solve the problem?

[fox]

Not sure what this means. If you rearranged your desk and physically reversed the position of the monitors, would that solve the problem?

It would and it wouldn't. Because of the location of the window, it wouldn't work well to take the extra monitor and move it to the right of the iMac. I suppose I could take the iMac with its internal monitor, move it to my left and put the extra monitor in front of me, but the iMac monitor is better resolution (1920x1080 vs 1680x1050) so I prefer it to be in front of me and used as the main monitor. Bottom line: if this is the only reason for my freezes, I can live with the non-intuitive moving of the mouse in the opposite direction to get it on the other monitor.

[fox]

Update: No freezes in two days with Unity and no Gnome3, display configuration left backwards and the default nouveau driver. Yesterday I briefly tried changing to driver to the Nvidia default (361.42 in Ubuntu 16.04) and no changes to the display configuration. The system booted into a desktop, but missing the Unity bar and I only had limited functionality. I could probably have gotten this to work had I reconfigured the monitors before changing drivers, but I didn't want to do two things at a time so I just removed the driver. Everything continued to work without freezes.

This afternoon I changed the display configuration so that dragging the cursor off the default monitor to the left gets it onto the auxiliary monitor to the left of the iMac. No freezes so far. Assuming it stays that way tomorrow morning, the next move will be to reinstall the Gnome3 desktop.

[fox]

Unfortunately, I got a freeze today with the display configuration matching my monitor setting. It happened in LibreOffice Writer like a lot of the previous ones. So I went back to the reversed display configuration, and got no more freezes. I also added back the Gnome desktop and worked on that for awhile, using the same programs. No freezes. So at this point, my most likely culprit is the display configuration. It takes some getting used to to move your cursor to the right to get it to show up on the monitor to the left, but it's better than having regular freezes, and better than disconnecting the auxiliary monitor. I'll have to spend some time googling to see if this problem has ever been reported.

[fox]

Adding Gnome I got more freezes, even when I used the reverse display setting. I tried a kernel update and the latest nvidia driver, but still had problems. So the only settings that kept the freezes away were Unity with no gnome, noveau driver and reverse display setting. I could live with this, but I'm not happy about it; not enough to stop searching for a better solution. Not doing anything until I return from holidays but the next move is to wipe the new partition and install Ubuntu 14.04. If that doesn't work, next would be openSuse Leap.

[fox]

Update. I installed 14.04 alongside 16.04 and had no freezing with it with nouveau driver and Unity. I didn't take it any further because there were certain apps I had to give up when going back to 14.04 (most notably Gnome calendars). Meanwhile, 16.04 seems to be fine with nouveau driver and Unity. I'm OK with both, so that's what I'm using. I consider the problem solved.

[bobf]

Jeez... I dunno, Mike... I think you should poke it with a sharpened stick some more. You know the motto: "If it works, you're just not trying hard enough!" <^8#

You'll get complacent this way... Ugh! <^8#

[fox]

Didn't have to "poke it" long; I did get a freeze two days ago, so the problem isn't entirely solved. But I can live with a freeze once in awhile, and that won't push me to change distros. Still I would like to know the cause. I'm just not seeing many reports of it by folks using a dual monitor setup and even those, not with a Nvidia card.