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ASRock X99 OC Formula/3.1 (Intel X99) Motherboard Review (Page 3)

By Steven Bassiri on Jul 6, 2015 03:13 pm CDT
Rating: 92%Manufacturer: ASRock

Circuit Analysis


The VRM on this board consists of 12 phases, but ASRock has further enhanced the power output of the X99 OC Formula/3.1 by doubling up on the normal number of MOSFETs they use for their 12 phase/1300W VRM. ASRock has focused on power density by utilizing lower profile 60A inductors and more integrated phases. The output filter is made up of 8x 560uF solid 12K Nichicon capacitors at 4480uF.


The PWM controller is an Intersil ISL6379 Digitally Controlled Hybrid 6 phase PWM. There is no datasheet, but I would venture to guess that it is a 6+1 phase PWM. To get 12 phases, manufacturers must double the phase count from the PWM since there is no 12 phase PWM in production for motherboards. ASRock uses 6x Intersil ISL6611A which are phase doublers with integrated dual drivers located on the backside of the motherboard.

This saves a lot of space which is important considering the limited motherboard real-estate of the X99 platform. ASRock is using 24x FDMS3668S which are dual N-Channel MOSFETs from Fairchild Semiconductor in the PowerTrench package. They have very good thermal and current ratings at 13A/18A (high/low side) at only 2.5W, which is excellent.


Each memory VRM is like a two phase version of the CPU VRM, using the same ISL6379 PWM and the same dual N-Channel PowerTrench MOSFETs for a total of three ISL6379 and 16 dual MOSFETs on the board. This is just one of two identical memory VRMs on this board.


An MPS MPQ8632 is used for the VPP power for each set of the 4 DIMMs. The memory DIMM's main MOSFETs need drivers and four tiny ones are found on the back of the board. The drivers are Intersil ISL6208.

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Steven Bassiri

ABOUT THE AUTHOR - Steven Bassiri

Steven went from a fledgling forum reader in 2003 to one of the internet's brightest stars by 2010. Armed with an information systems degree, a deep understanding of circuitry, and a passion for tech, Steven (handle Sin0822) enjoys sharing his deep knowledge with others. Steven details products down to the component level to highlight seldom explained, and often misunderstood architectures. Steven is also a highly decorated overclocker with several world records under his belt. He brings that knowledge and experience to TweakTown.

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