Will chipset drivers for AMD 770/SB700 be backwards compatible with chipset AMD 770/SB600? I replaced an ASUS M3A78 board with M3A and it didn't come with driver disk and ASUS isn't providing any.
They should be. The last driver update for any of the 7X chipsets was 15.7.1. You can download it from 790GX Drivers & Support | AMD
So as long you have a recent version you should be good with any 7x chipset.