@Stephen23

Thanks for your post on the G.Skill HZ's.
I just received my replacement 6400 HZ's and noticed the PCB was black and I was sure the dead ones (RMA'd) were green.

Unfortunately I can't push them very far due to CPU cooling issues (good ducted TTBT air setup, good general air flow, but no RAM cooling) but given that the temp in my office has dropped by about 7c, I could try to push them a little further than their current 1:1 438 4-4-4-12 2.1v (suggestions welcome ).

I'm still a little unsure which are/were better; the original Green PCB version or the replacement Black PCB version?

Cheers