Originally Posted by Cyrious
Overclocking ram is entirely dependent on the structure of the CPU-RAM-northbridge layout and what options the BIOS gives you. On some systems, the RAM is run on its own separate clock generator, allowing it to run somewhat asychronously from the rest of the system. On others, it is locked to another part of the system, typically the FSB.
On your system, your ram is run on its own dedicated clock, and thus that gives you the option to overclock as you see fit.
On older systems, typically ones using the classic setup where the memory connects to the chipset instead of the processor, you had to worry about ram dividers. Memory, then and now, cannot usually run 1:1 with the system bus when said system bus is running at a high clock rate. The memory chips cannot handle it. So what is done instead is that the memory clock is put through the divider to slow it down to a more acceptable rate. For example, on my sig rig, if i were to leave the memory divider at the default speed, and the FSB at the default speed, a 1:1 divider would have my FSB running at 800mhz (rated) and the ram running at a 800mhz (rated). For every bus data pulse, there is one on the ram as well. the ram us running Synchronously.
As i increase the FSB while maintaining the 1:1 divider, the ram speed increases in lockstep as well. And then i reach about 920mhz rated on both the FSB and the memory. My memory can no longer handle it, and thus in order for me to continue increasing the FSB to increase the core clock, i have to slow the ram down. To do this, i would have to select a different divider, say, 3:4 (DRAM:FSB). So for every 4 ticks of the FSB, there are now 3 ticks for the ram, slowing it to a sedate 690mhz. Now i can drastically increase the FSB while keeping it within the memory's limits, allowing a 1333mhz rated FSB.
On your system, as i have mentioned before, the Ram is not tied to the FSB, and as far as i know can be overclocked independently of the other system settings. 1866mhz rated is a popular setting on Sandy-bridge based systems, and you should be able to get it up there.
As for requiring extra cooling, when you have met your ram overclocking goal, tightening the timings for extra performance will often need extra voltage, especially if you are going to do it at 1T settings. Increasing the voltage, and tightening the timings are the 2 things that will increase the heat output. On moderate setups, just getting some extra airflow through the case and thus over the ram is more than sufficient to keep the ram cool and running fine. On extreme setups and using very very high end ram (such as Corsair Dominators or Kingston HyperX ram), active airflow over their oversized heatspreaders is needed when taking them to their limit. It all depends on the situation, the memory modules being used, and sometimes the chips on the modules themselves.
Word of advice: dont go overboard on the ram voltage. Too much voltage to ram will result in rapid degradation unless the chips and modules have been binned for them. You can usually figure this out by checking the specs on your particular set. A little extra voltage is OK, usually 10% more is not harmful, but 18-20% and up is the danger zone.