Ram Speed - Does motherboard or CPU limit ram?

[Exerion09]

If I have a CPU that has maximum supported ram speeds of 1866MHz and 8GB of 2400MHz ram, can I safely keep the ram at 2400MHz if the mobo supports 2400MHz? or do I have to throttle the ram to something more reasonable like 2133MHz?

*I got a really good deal on 8GB G.Skill Sniper DDR3 PC3-19200 2400Mhz and haven't picked out a CPU yet but want to be under $130 if possible.

Thanks

 

[Spath87]

The motherboard dictates the RAM speed. Even if you use 2400MHz RAM, your motherboard will bring it down to whatever its rated at.

 

[brispuss]

Actually it is the combination of CPU and motherboard which limits DIMM speed. DIMM speed will only go as high as the lower of the speed limits between the CPU and motherboard.

For example, a CPU may support speed up 1600, and a motherboard supports speeds up to 2400, but the DIMM's will go up to 1600 (stably).

 

[Tradesman1]

The mobo needs to support the DRAMS data rate but the CPU is the key (specifically the MC in the CPU), i.e. for 2400 - all Z97 mobos will take 2400 sticks (including the Sabertooth which advertises 1866), but to run 2400 (at spec anyway) you will need an appropriate Intel 'K' model CPU. A few non-K might run 2400 with loose timings