Locate the Fallout 3 New Vegas settings folder in “My Games” change the fallout.ini file (remove read only property)
Find the following line:
bUseThreadedAI=0
change it to:
bUseThreadedAI=1
Add your own line underneath and insert:
iNumHWThreads=2
Maybe this will work for you? It worked for me in Fallout 3.