I've been stalking this thread for about a month now and I've finally decided to contribute a bit
The RAM kits I am using are excessive... 2 x CMK32GX4M2B3200C16 = 64 GB
I have managed to get 2667 on 1.4 on 4 DIMMs but there was some instability. Sound went flaky and icons on the desktop randomly refreshed. Benchmarking and gaming didn't have any particular problems, but Skyping while gaming was very poor quality (a lot of glitching and distortion). I'm sure it's not a connection issue, because if I'm outside the game Skype is crystal clear.
I'm using 1.5 now and 2667 seems a lot better with a bit of tweaking. Task Manager says the speed is 2133 (2 x 1067), but CPU-Z insists it's 2667 (2 x 1333) and User Benchmark seems to confirm between runs (http://www.userbenchmark.com/UserRun/3528716
I had to up the voltage to 1.37, NB to 1.1 (although as the video says, it shouldn't matter) and input manual timings as the [Auto] defaults to weird values.
My CPU is a 1800X overclocked to 4.0GHz on 1.375V. It can do 4.1 at around 1.45V, but I don't see the point since it generates quite a lot of heat and I'm air cooling (6 case fans + Noctua NH-D15).
Hopefully we can get 2933 on 4 DIMMs at some point using 'generic RAM kits', I'm not getting my hopes up for 3200. Edited by dreadrazor - 4/28/17 at 3:03am