t7500 not using all cpu cores after motherboard change

I recently had an issue that prevented my T7500 precision desktop from getting passed loading the BIOS.  I replaced the motherboard and the computer seems to be working, however only 12 of the 24 cores are now active.  I had assumed this was because the expansion card wasn't connected, but the computer is reporting all 48 GB of memory. So its seeing the memory on the expansion card just not the 2nd cpu.  Any suggestions would be helpful.