Folding Forum

I have a Windows PC running with two Xeon E5-2660 V2 processors. That's 20 cores and 40 threads. FAH client only recognizes 32 threads. Why? Also, I have two R810 Linux servers that have 80 threads each. I haven't yet installed FAH. Will FAH be limited to using fewer than max threads? Please advise. Thanks.

Welcome to Folding@Home!

There are issues with more than 32 threads (F@H calls them CPUs) in one slot

You can make multiple CPU slots however, and use them all!

You will just be doing more than one Core_a7 Work Unit at the same time.

So if you have no GPU folding you can have a slot with 32 andd a slot with 8. (Later 80 is 32, 32, and 16)

In the taskbar to the lower right of the screen, you should see a F@H molecule icon, click it (you may need to click an Up Arrow to see it ^)

The second item in this menu is Advanced Control, click it

On this screen to the left is a Configure button, click it

Now you get a screen with a Slots tab, click it

On this white field should be a cpu item, click it and then click edit

By default F@H set the number of CPUs to -1 meaning let the software decide.
You can enter any number from 1 to the number of threads your CPU supports.

If you have GPUs, F@H reserves one CPU per GPU to feed it data across the PCIE bus.

F@H has difficulty with large primes and their multiples number of CPUs.
7 is always large, 5 is sometimes large, and 3 is never large. Try to choose a number that is a multiple of 2 and/or 3.
2, 3, 4, 6, 8, 9, 12, 16, 18, 20, 21, 24, 27, 30, 32 are good numbers of CPUs to choose. (_r2w_ben has advised me of more good numbers)
5. 10. 15, 20, 25, 28 may work most of the time. Other numbers will bite you
Type the number you want, and click save.

F@H may have issues with CPU counts over 32, if I had more than 32 CPUs, I would make multiple cpu slots. There is an add button on the Slots screen.

32 threads is a Windows limitation that depends on the Windows license installed, and how the program that will use multiple CPU threads is created.

For Linux you will not run into that limitation. However some high thread counts will not be used due to decomposition issues of the simulation. At times there CPU projects that will uses as many as 80 threads, at other times the WUs may be harder to get assigned. You may run into some issues that persons here on the forum have run into before with high thread counts, if you post here they may be able to help.

Thank you. I now have 2 CPUs with 20 threads (CPUs) each.

A 32core slot and an 8core slot would do quicker science and get you more points ... 20core slots may have more issues as divisible by 5 which has in the past been worth avoiding.