I am quite sure that this may have been asked about in the past, so if this is the case just please direct to the answer and I'll try and stumble on from there.
The Asus rampage iv extreme has 2 ez plug sockets. one is for a 6 pin plug to supply additional power when using 4xgpus. the other is to supply additional power to dimms. The manual makes no reference to the type of plugs that go in these sockets, nor could i find anything on the asus website.
For example, the 6 pin socket could take one side of a 4+4 plug or it an take a 6 pin plug similar to that which goes to the gpu cards. Both of these have different pin outs where the 12v and 0v rails are on opposite sides when compared to each other.
The 4 pin male socket on the board has a plastic backing that i am not familiar with (just looks like a thin plastic wall) and I cannot readily match it to most known cables (it may be that it does but i just cannot see the matching female plug).