Are these compatible?

The CPU support list for that board can be found here
http://www.foxconnsupport.com/cpusupportlist.aspx?type=mb&model=A78AX-S&cputype=

Strangely it supports all of the AM3 Phenom IIs but not the AM2+ PII 940. You could use a 945 or a 955 in it and it should work.