And what is the 740g? I put 740g into Google and got a John Deere Loader Backhoe - but I'm assuming you've got one of several manufacturer's motherboards that use this in the model name and have the AMD chipset of the same name?
Regardless... I can't see any AM2+/AM3 motherboard capable of using the Phenom II CPUs having a bottleneck in those conditions. Systems don't mind being underutilized - ask mine!