I can test 7-Zip in the GUI and get it to see all 16 Cores, but I can't see to get the Command Line right. Here is what I'm testing out edited for public viewing:
7z a -t7z -mx=9 -m9=LZMA2 -mmt=15 "C:\Destination.7z" "C:\Temp\*.*"
I'm specifying LZMA2 since that's needed to enable the multithreading from everything I've read. What's off?