Hi, I´m planning on buying an intel i7 4930k cpu, an asus rampage iv black edition motherboard and 16gb of corsair vengeance pro ram, my cpu supports 1866mhz and my motherboard supports 2800mhz wich frequency is the best, does it depend on the cpu or the mobo? Tx in advance!
Speed of the RAM depends on one, frequency and two, on latency. Generally, as the frequency increases the latency decreases and vice versa. Therefore, try to get the sweet spot between 1866mhz and 2800mhz, as you will get the best value for the money you spent. And as for the other question, it depends on the motherboard. Hope that helps!
Big thing is what you will be using the rig for, the high freqs won't help gaming as much as they will help performance in things like video, imaging, VMs, CAD, muti-tasking etc....for most 1866/8 or 9 to 2133/9 are very good in a 4x4GB config (to allow use of full quad channel operations)... For the X79 platform would suggest the Ripjaws Z or the Trident X models from GSkill, their Sniper line would also be a good choice
Tx I was planning to purchase the 1866mhz its supported by the motherboard and cpu, I just wanted to now if getting the 2800mhz would be incompatible or bring any problems.
If your mobo supports it and you have the budget for it, yes, you can go for it. But given the price increase after 2400 MHZ is too steep as compared to the performance increase, so 2400 or 2133 is recommended. Even the cheapest 2800 is about $230 as compared to the 2400 which sits at $ 75 while the performance difference isnt worth the price paid.
The vengeance will work, but at 2133 and CL11, can get better pricing/performance from a 1866/8 or 9 set, if going 2133 look for CL9, the Trident 2400 set suggested by Verma1891 would be a good set, they also come in 2133/9 and 1866/8 as I suggested earlier