OC'ing RAM is done in the BIOS on boards that support it by setting the RAM clock speed and timings higher than stock. Intel XMP must be enabled to run RAM at higher speeds for Sandy Bridge because the internal memory controller works at 1066 or 1333. You can get RAM that is higher speed but make sure voltage is 1.5V or lower and XMP is enabled. It's really safe to only pick RAM that says "Intel XMP ready" or "designed for Sandy Bridge" but no matter what, running RAM faster than CPU specs voids the warranty.
There really is no real world difference between 1333mhz and 2133mhz, some ram won't oc.
Additionally, as mentioned in a number of articles on Sandy Bridge memory testing, you won't see much of a hike in performance past 1600 anyhow so using 2133 is a waste of money and can potentially cause stability issues.
>-Cant you overclock RAM? Is it like buy a high end processor and pushing it further
Technically yes, but usually no. Headroom in DRAM is significantly lower than the headroom in CPUs. You'll be lucky to get more than 5% out of non-enthusiast DRAM kits. So while it's possible to overclock DRAM beyond its marketed speeds, it's usually not worth the time that it takes to get it stable at high speeds
-Can you not OC RAM and your just OC the processor to run it at stock speeds.
Back in the days all the system components were linked to a single clock generator. Speedstepping didn't exist which meant that everything ran at what was more or less a multiple of the system clock, DRAM, CPU, PCI bus, System bus, etc... all included. Since CPU PLL clock multipliers were historically locked on all but the most expensive models (sometimes they were locked in a way that made them easily unlockable, but no more) this meant that in order to overclock the CPU you also had to overclock everything else. Overclocking the system buses was historically quite easy as there was always a lot of headroom on all of them. However, the DRAM did not have a lot of headroom which drastically limited options. The usual response was to change the PLL clock multiplier on the DRAM controller to a lower value, such as from 2:1 to 3:2. 4:3, 5:4 or even 1:1. While this allowed the CPU to be overclocked more than it would with the standard DRAM multiplier, it drastically cut the performance of the memory which at the time was a much more limiting factor than it is today.
There were two ways around this. Either buy higher quality DRAM that works at a higher speed and allows you to keep the stock DRAM multiplier or buy a motherboard with a separate clock generator. The motherboards with a separate clock generator sucked horribly, and since DRAM controllers are entirely on-die now they're no longer in production. It's also much easier to select DRAM speeds independently on newer platforms which entirely removes the bottleneck.
So what's the deal with high-speed DRAM? It's mostly just a gimick, as others have said it really doesn't impact performance much beyond the 1600MT/s (800Mhz bus speed) barrier. Throwing in high speed ram with XMP profiles will usually work quite well, Intel's DDR3 controller team has really done an excellent job. I'm running 32 GB of DDR3-2133 DRAM on purely XMP and Automatic settings, a similar feat with an off-die DDR2 controller would be unattainable. There are a few benchmarks showing the performance of different memory platforms and high speed memory doesn't really fall behind in any of them and in some it can actually show a clear advantage.
>When you buy 2133 Mhz stock speed RAM
>-and your mother board RAM support is as follows 2133(OC) / 1600 / 1333 / 1066 / 800
>http://www.newegg.com/Product/Prod [...] 6813157271
>What are the steps to run the RAM at stock speed
RAM always runs at stock speed out of the box. Typically it will default to 1333. If you want to turn on the overclocked profiles (1600,1866,2000,2133) you need to either enter them manually or select the XMP profile in the system setup. Please note that 2133Mhz ram will put a lot of stress on your CPU, especially if you run a large amount of it.