DDR3 SDRAM Overclocking in LGA 2011 Systems
Regular Sandy Bridge processors officially support DDR3-1067 and DDR3-1333 SDRAM. Sandy Bridge-E processors also acquired official support for DDR3-1600 SDRAM. However, the processor memory controller in both, LGA 1155 as well as LGA 2011, has much more dividers, which allow clocking the memory at even higher frequencies. Speaking of Sandy Bridge-E, we can say that this processor allows configuring the memory as DDR3-1867, DDR3-2122 or even DDR3-2400 SDRAM. Almost the same was true for the LGA 1155 systems, but the new LGA 2011 boast yet another feature – they allow changing the base clock generator frequency, too.
Unlike LGA 1155 systems, the new LGA 2011 platform uses an enhanced clocking algorithm for the CPU and all connected system knots, which allows the user to set the BCLK frequency not only the standard 100 MHz, but also to 125 or even 166 MHz. The frequencies of the system busses and controllers do not change in this case, but the CPU and all other units in it get proportionally overclocked. So, it also refers to the memory controller: by setting higher base clock generator frequency, you get wider range of supported memory frequencies to choose from.
This way the LGA 2011 platform offers more flexible memory overclocking than LGA 1155 platform. For example, if you use the additional supported BCLK frequencies, you will be able to get memory frequencies with an increment below 266 MHz. Moreover, you can set even higher frequencies than before. And the use of high-speed DDR3 SDRAM doesn’t pose any particular problems. If your system is equipped with four DDR3 SDRAM modules, operational modes up to DDR3-1867 will be available to you without any additional effort. With eight modules in the system this maximum may be lowered to DDR3-1600.
However, even if you get to the point when you need to make some “effort”, it doesn’t imply anything extraordinary. To ensure stability of the system at higher memory frequencies, you may need to increase the VTT voltage on the memory controller or the VCCSA voltage on the processor system agent, or even on both. Overclocker memory makers recommend using pretty high settings for these voltages, and sometimes they even record them in the modules XMP profiles. They really help a lot during overclocking. However, during our conversations with Intel we managed to find out that only the increase to 1.1 V on VCCSA and to 1.2 V on VTT may be considered “safe” for everyday use in 24/7 mode. Moreover, you should also keep in mind the recommendation not to exceed 1.65 V for the memory voltage, otherwise, it may stimulate degradation of the memory controller and untimely death of your processor. However, you can almost always reach DDR3-2133 frequency even without using the “risky” settings.
In this respect I can’t help mentioning that the manufacturers of overclocker memory were very excited about the new LGA 2011 platform. Many companies started offering not only quad-channel DDR3-2133, but even DDR3-2400 memory. However, purchasing high-speed modules like that can only make sense for benchmarking applications. For example, with DDR3-2400 you will most likely have to use very unsafe voltage settings. Moreover, I am sure that not all mainboards can handle memory working at this high frequency. However, there shouldn’t be any problems with DDR3-2133 and this memory will be a perfect fit for contemporary high-performance desktop systems.