This took a bit a searching, but one model is a x4 and the other is a x8.. I gather it's some sort of speed rating? or maybe just an indication of the model.
- Chipkill is described here. (Search the page..)
- SDDC likely refers to Intel SDDC(Single Device Data Correction), a few hits are available on Google.
I'm pretty sure it means the x8 model does not support these features.
I hope that helps pal.