On the previous page we observed that the high memory speeds were probably being bottlenecked by the 3000Mhz uncore processor speeds. At the moment only two ASUS boards, both being equipped with the OCing socket are able to push the processor Uncore easily over 4000Mhz. All other boards are maxing out on air at 3500-3700ish speeds. For a daily user the latter are no real limitation, though for the efficiency tweakers at the moment there are only two viable options: The ASUS X99 Deluxe and the Republic of Gamers Rampage V Extreme.

The brave can try out the Der8auer's Guide for Haswell-E 4GHz+ Uncore (For All Motherboards)

The experienced guys can do his lazy mod pretty easy providing an uncore voltage of around 1.26, good for 4000-4500ish speeds. Take note that any of these modifications will void your warranty!!

Back to the testing: We used the i7-5960X with the full 8 cores enabled. The DDR4 memory speed was limited at 2666Mhz C15-15-15-35 with a 2T Command Rate set.

We tested the uncore speed at 3000MHz, 3500MHz, 3750MHz and 4000MHz speeds. Any X99 board can handle the first two uncore speeds, from 3600ish speeds on the two aforementioned ASUS boards will have the edge and will even go above +4500MHz (depending on the processor limit)

In SuperPi 32M we see a massive gain in performance by gradually increasing the Uncore speed of the processor. Higher uncore speeds of 4500MHz were also possible though required upping the cache voltage; fine for benchers though for those that want to max out their daily setup with safe voltages can easily achieve 4000MHz on the two former mentioned ASUS boards. Even with the memory just running at 2666MHz it beats the scores of the 3000MHz DDR4 setup with over 4 seconds. Conclusion: when running high memory speeds, one needs a high uncore speed to lift the bottleneck and to maximize the performance of your setup.

The AIDA64 Bandwidth test shows what really happens: not only do Read and Copy progress with higher uncore speeds, also the Write performance receives a significant boost. Confirming our theory that indeed boosting the uncore speed is a must to achieve the best performance of your favorite Haswell-E processor.

While Cinebench R15 scaled very mildly with the increased memory speeds and not touching the uncore. Boosting the uncore has a drastic effect on the performance in this benchmark; even in the synthetic 3D benchmarks a small gain is each time noticeable once we increase the uncore speeds.

Gaming wise there is hardly any influence with the standard uncore speed of 3000MHz or the overclocked one of 4000Mhz. Alike the lack of increased memory frequency will have hardly any impact on your gaming experience.