R9 290X VRM design specifications run down.

MSI R9 290X Lighting Physical phases: 12+2+3
Controller: IR 3567B 6+2 for the core and auxiliary. I can't find the memory voltage controller without having the card in my hand. You get control over the 3 key voltages and then you gotta pray that MSI's BIOS and AMD's drivers won't screw you over.

ASUS R9 290X Matrix
12+2+2
Controller: A re-branded  IR 3567B 6+2 0.2Mhz-2Mhz for the core and auxiliary. I can't find the memory voltage controller without having the card in my hand. This is the only card that will let you manually tune the controller's operating frequency and all voltages that exist on an R9 290X.

ASUS R9 290(X) DirectCU II
6+2+2
Controller: A re-branded  IR 3567B 6+2 0.2Mhz-2Mhz for the core and auxiliary. I can't find the memory voltage controller because I never had the chance to take the card apart.

Sapphire R9 290X Vapor-X
12 total 8+2+2
Controller: IR 3567B 6+2 0.2Mhz-2Mhz. The 8 phase design is very likely not a true 8 phase design and is using doubler but luckily for anyone reading this blog I'll be getting a sample so I'll have exact specs then.

Sapphire R9 290 Vapor-X
8 6+1+1
Controller: IR 3567B 6+2 0.2Mhz-2Mhz. 6 Phases for the core and one for auxiliary. Memory has it's own static voltage controller. Unfortunately all the 71A MOSFETs of the AMD reference design have been replaced by 40A IRPowerStages leaving you with only 240A of current for the core and 40A for the auxiliary. The memory still uses the 71A MOSFETs.

ALL other models
5+1+1
Controller: IR 3567B 6+2 0.2Mhz-2Mhz for the core and auxiliary. I can't find the memory voltage controller because there isn't one, no really there isn't the voltage is 1.5XXV idle and drops to 1.4XXV in load which got me really confused when benchmarking Unigine one time.

BTW I will be getting the parts for my AMD rig tomorrow so prepare for even more reviews and guides.