Have a old quad core system that I've had since Fedora 10 I believe.
Recently, upgraded to Fedora 31, and it was still seeing all 4 cores.

Run BOINC, and recently notice that it was only showing 3 cpus
running? Machine is one of the 5 computers I have at house, but is
headless and access remotely via VNC. Other systems all show the right
number of cpus after updates, so not sure what might cause the issue.
The results of lshw-gui shows the 4 cores, but the dmesg shows only
CPU 0 - 2. Didn't notice this until the 5.7 kernel change, but not sure
exactly which update caused the change.

Any ideals what could fix this, or how to get specific reasons it might
have happened. Other machines are newer, some dual and one other
quad core. So, just this one??

> This is not a 5.8-rc3 problem. Almost all AMD CPUs and APUs are
> looking like this.
> The only CPUs I own are getting that right is a dual EPYC box,
> everything else is broken
> regarding the right C/T & socket(s) count, and that probably bc is
> using NUAM [sic] code
> to have the info.