DDR3 PC3-12800 vs DDR3 PC3-10600
Will the two 4GB RAM modules from a late 2012 iMac (DDR3 PC3-12800) work OK if installed in a mid 2010 iMac (comes with two 2GB DDR3 PC3-10600)?
iMac, OS X Mountain Lion (10.8.2)
Probably not. The worst thing that could happen if you try is the computer will get a Kernel Panic and damage OS X though.