Hi!

Both were set. Use at most 30% of CPUs and 80% of CPU time if I recall correctly.

Task manager was reporting 100% of all CPUs used. which is what led me to believe that some project was starting more than 1 thread somehow.

SiDock@home use 1 thread for compute per tasks. If I set 50% of cores on my Ryzen 3900X, BOINC runs only 12 tasks. As I see, control of % CPU time per core is more hard task than control of number of running cores. Actually in 8*dt process used 100% of core and in next 2*dt - 0%. Setting only number of cores percent (for example 25% instead of 30% of cores with 80% of CPU usage) looks like problem solution with more predictable result.

It appears that the 80% of CPU usage is over all of the cores, not per core.

Task Manager (a Windows System Utility) was reporting 100% CPU usage on all cores on the device (not just the cores that were allocated to BOINC). I had BOINC Manager running behind Task Manager so I could see some information in BOINC Manager as well. I watched Task Manager bounce between showing 100% CPU usage across all cores (every core running flat out) and less than 10% total across all cores (Which could be 2 cores running nearly full out, or a small load on each core - Task Manager isn't that specific). When BOINC Manager reported all tasks suspended, the CPU usage total was < 10%. When BOINC Manager reported all tasks running, Task Manager reported that total CPU usage was 100%.

Something is clearly taking more CPUs that it is supposed to. Since disabling this project made the problem go away, evidenced points to this project as the culprit. I'm wondering if there is some library that you are using that might start extra threads under some conditions. I know that multithreaded applications are a pain to debug as they tend to generate heisenbugs. I didn't notice if you used a container of some sort. If so, it might be some interaction with the container.

Computation module use only one thread per each task.
Preferences, mentioned above described as:
Computing:

Usage limits

Use at most N % of the CPUs: Keeps some CPUs free for other applications. Example: 75% means use 6 cores on an 8-core CPU.
Use at most N % CPU time: Suspend/resume computing every few seconds to reduce CPU temperature and energy usage. Example: 75% means compute for 3 seconds, wait for 1 second, and repeat.

If, for example, computer support 16 threads, and preferences set to 25% of CPUs and 50% of CPU time, BOINC will run 4 threads in 50% of time and suspend it in another 50% of time.
But special setting of modern computers pointed on saving of power usage can confuse everything. Frequency reduction, transfers of cores into C6 state e.t.c.
When I setup of computer for BOINC, firstly, I turn off overclock and energy save options in BIOS and OS.
If you want to reduce CPU heating, set "Use N% of CPU cores" and return "% of CPU time" into 100%. It's more reliable. May be - restart BOINC also.

Also, I can imagine, that due some settings of computation or sharing resources between projects, BOINC start some computing processes and they become orphaned and uncontrolled. But if this is case, you, for checking, can reduce situation to more simple: only 25% of CPUs, and only SiDock@home project. And check the work. This experiment can explain some things.

That does not match what I was and am seeing.

Anything?

Hi!

To clarify the situation:
1. Disable in BOINC Manager all projects except SiDock@home;
2. Set "Use at most N % CPUs" to 25%;
3. Set "Use at most M % of CPU time" to 100%;
4. Stop BOINC;
5. Check, that CPU usage is 0 % (if not, make a screenshot [1] of tool like Process Explorer with processes, that consume CPU and its threads);
6. Reboot computer;
7. After starting computing (only SiDock@home should start), make another screenshot from Process Explorer [2];
8. Post links to screenshots [1] and [2].

Ok. We have a heisenbug. If I just sit looking at the computer waiting for it to happen, nothing happens. If I start using something with the mouse where I am doing actual work, I can see BOINC Manager shutting down and restarting the application in the background, and the computer gets horribly laggy, as in the mouse can freeze in place for a second. This does not happen with any of the other projects that I run under BOINC. I have captured the screenshots of prior, but cannot get a screenshot of what happens when it freezes because when I go to look, it is back to normal. I am about ready to give up. Please note that i am not the only person that has complained about this.

I can see BOINC Manager shutting down and restarting the application in the background

Clearly not what should be happening.
Looks like WU's crushing or constantly suspending/restarting.
Have you any conditions in "When to suspend" section configured?

Yes, check settings like "Suspend".

Suspend when on batteries is the only item checked in that block (and the computer is plugged in and the lights are on.

Would you post the links on screenshots, that you made?

Still no problems with any other project using far more than the allotted CPU. Something about this project is using more than one thread when anything else is done on the computer (such as mouse move). No, I can't get screenshots of the problem. Much as I try, the machine is locked up so hard when this happens that nothing works, not even the keyboard.

It is still on no new work.