I don't think it's bytewise (just like nobody does RAID3), but, yes, they can and do. The keyword you're looking for is "interleaving". I think it's also not e

I don't think it's bytewise (just like nobody does RAID3), but, yes, they can and do. The keyword you're looking for is "interleaving". I think it's also not even by DIMM slot but by channel, so if the channels are unevenly populated (e.g. 2 slots filled on one channel but only 1 on another), interleaving is disabled.