Hi, please allow a suggestion:
940/ AM2+ may have the same die layout as 945/ AM3 at the same stepping but with different schemata of connections between die and socket pins. Because of that all 9x0/ AM2+ could only work with DDR2 but all 9x5/ AM3 could work with DDR2 or DDR3 each at one time but not together. In the case of 9x5/ AM3 it only depends on the mobo with its BIOS and if the mobo supports free memory choice DDR2 and DDR3 it depends on installed memory and configuration which IMC will be used and actively connected through socket pins.
The main difference between AM2+/ AM3 CPU is that in AM2+ CPUs only the IMC for DDR2 is connected to the outside (fixed) - may be the other one is on die, too, but not connected to socket pins furthermore AM3 CPUs have two full functional and connectable IMCs - for both, DDR2 and DDR3, too, and both can be connected alternatively to outside through socket pins.
Please correct me if I'm wrong. Thx.