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While a board’s PWM/MOSFET count generally indicates its capability to handle a particular load rating, it does not always indicate its ability to properly regulate, correct, and deliver clean power. That is why a board with a properly designed four-phase system can offer improved quality/performance over a poorly designed five- or six-phase system. All of our boards in the roundup utilize a decent three- or four-phase PWM design, with the exception of the ASRock board that features a five-phase design. Does this mean that the ASRock board will handle the 9850BE without a problem? Not necessarily, as there is more to our story than PWM design.
The critical aspect of running a 9850BE at stock speeds on the current 780G boards centers on the cooling of the PWM circuitry. Each and every manufacturer along with AMD agreed that cooling the MOSFETS properly was critical to the successful operation of the board at stock or overclocked speeds with the 9850BE - and to some degree, the 6400+ X2. The lack of space around the CPU area in the uATX design results in a crowding of components leading to additional thermal loads. This type of thermal loading is not prevalent in most ATX designs utilizing similar PWM components or the space that an additional/improved phase design (with associated components) affords.
We have measured MOSFET temperatures ranging from 128C~146C utilizing the stock CPU cooler on the 9850BE in our Silverstone SG03 case (temps were about the same in our Thermaltake and Zalman cases). While cooling of the PWM/MOSFET area is critical, most of the manufacturers admitted that improved component choices and electrical layouts similar to the 790FX boards is also required to ensure a robust design for users who are on the more enthusiastic side. However, this means additional costs that would place the board out of its intended market, a market where probably 98% of users would not worry about running a 125W TDP processor. For those who demand this extra level of performance, we expect to see several 780G ATX designs in May offering improved PWM designs.