I notice in running all work that for some reason Boinc is reluctant to utilise cores 4 & 5 supporting processors 8,9,10, 11. In checking performance monitor those processors show very low usage, single figures while all the others are very high. I generally run at 50 or 75% for Boinc.

Any ideas why Boinc won’t use these cores/processors please. I have run the Intel test programme and everything is fully functional.

Thanks

In reply to Hadrian's message of 24 Jan 2026:

I notice in running all work that for some reason Boinc is reluctant to utilise cores 4 & 5 supporting processors 8,9,10, 11. In checking performance monitor those processors show very low usage, single figures while all the others are very high. I generally run at 50 or 75% for Boinc.

If you limit the number of cores/threads available to BOINC then it can't use all of them.

---

Grant
Darwin NT.

Thanks, have now done a hours at 100% and it does use the cores. I wrongly assumed that Boinc was perhaps a bit more sophisticated than it is in processor scheduling.

In reply to Hadrian's message of 24 Jan 2026:

Thanks, have now done a hours at 100% and it does use the cores. I wrongly assumed that Boinc was perhaps a bit more sophisticated than it is in processor scheduling.

BOINC client relies on kernel scheduler.

---

BOINC maintainer.
For any insight, check my BOINC Development Blog.

In reply to Hadrian's message of 24 Jan 2026:

Thanks, have now done a hours at 100% and it does use the cores.

???
There are two different settings.

Use at most 100 % of the CPUs

This limits the number of cores/threads available to BOINC.
Usually anything less than 100% is unnecessary as BOINC applications generally run at the lower priority levels.
If a particular application running on a system is affected by running BONC Tasks, then you can free up some cores/threads by reducing the "Use at most" percentage, rather than using the "Exclusive applications" option.

Use at most 100 % of CPU time

Is for systems with poor cooling.
If actually fixing the problem with the cooling isn't an option, then reducing this percentage will reduce the CPU load, at the cost of significantly increased processing times for your Tasks.
If heat is an issue and the cooling problem with the device can't be fixed (eg current laptops/ ultra laptops), then it's better to make use of "Use at most xxx % of the CPUs" to limit the CPU load than "Use at most xxx % of CPU time" as thermal cycling is not good for electronic devices. And as i mentioned, it results in significantly increased processing times for your Tasks.

I wrongly assumed that Boinc was perhaps a bit more sophisticated than it is in processor scheduling.

???
If was doing what you allowed it to do. If you don't allow it to use all the available CPU cores/threads, then it can't.

---

Grant
Darwin NT.