Aristotelian: From what I read Broadwell E's shrink to 14nm includes improved memory management with the controller having DDR4-2400 capability vs DDR4-2133 capability in Haswell E.
Obviously DDR4 ram can be overclocked but this spec improvement alone seems to indicate support for much higher ram speeds.
I would hope that clock for clock Broadwell E is faster than Haswell E, the question is how much more.
Finally, it sounds like you are building a whole new rig. Do you have the custom cooling ready to go?
I have read about the improved memory controller too because there have been quite a number of posts complaining about memory speeds with Haswell-E, especially with boards like the ASUS X99-e WS, where it was clarified that the memory speed (overclocking) is partly dependent on the property within the chip itself. From benchmarks I have seen on this forum (e.g., does RAM speed matter? type threads) it seems that over specific levels (e.g., 3000), the increase in DDR4 ram speed will eventually be offset by the increased latency at those high speeds and - furthermore - that the increase in RAM speed brings a negligible performance boost. So around the time when I build for Broadwell-E I'll probably create a thread in the memory subforum asking for help finding the blisteringly quick 3000 or so speed ram.
At this stage - for someone like me about to build an entirely new rig, I'm drooling and waiting for Broadwell-E reviews which I hope come soon. I know there are probably people reading this who are under NDA, but I wonder if it violates an NDA to even hint at when the NDA period finishes?
[Off-topic disclaimer] Yeah - I am building a whole new rig man, completely watercooled - and thanks for your contributions in the other sub-forum in that 'ultimate water cooling setup' thread. I am working with one of Europe's best modders to build a bit of an artistic thing, but there'll be 3x480mm radiators (EK), 16 GT 1850 rpms (only one rad can fit 8 in push/pull in the Core X9). The radiators are really thick man and even in that case I'd have clearance issues if I did all the radiators in push pull fan setups.[/end]
So the Broadwell-E will go under a fairly ambitious watercooling setup and I'll look to people here (and elsewhere) for tips on pushing it to its most stable limit! As Adamk47 would say - Broadwell-E and Pascal/Polaris coming soon is going to put a major dent in my wallet. And my wife would have my head if I bought the new Dell OLED at the same time. Luckily, OLEDs seem to be coming out around Christmas, so I can gift one to myself due to a negotiated marriage clause And I'll stick with the Dell U2711 until then (lol!)