Intel's high-end desktop platforms can be finicky beasts, and X299 is no exception despite its roots in Intel's enthusiast-desktop chipsets. I'm not going to name names, but the breadth and depth of CPUs one can install on this platform seems to have stretched some first-run X299 boards past their limits. I've had boards crash entirely when benchmarks like AIDA64 try to execute AVX-512 code, for example—a flagship feature of X299 and its Skylake-X CPUs. Others can't handle Intel's highest-end Skylake-X chips without a fan directly on their VRM heatsinks to prevent overheating, even when chips aren't overclocked. In short, X299 has fallen a bit short of the expectations we hold for high-end desktop platforms, especially when compared to the stability and reliability we've seen from AMD's X399 boards.
One X299 motherboard in the TR labs has stood out from the pack for its unflappable demeanor, though. Much like AMD's motherboard partners have had to do in preparation for second-generation Ryzen Threadripper WX chips, a number of Intel motherboard partners released refreshed X299 boards earlier this year to better handle VRM cooling and the demands of 12- to 18-core Skylake-X CPUs. Gigabyte's X299 Designare EX is one of those boards, and it has been pleasantly problem-free with any Skylake-X CPU and memory kit I've dropped in its socket and slots over months of testing.
Gigabyte's X299 refresh mojo starts under the Designare EX's VRM heatsink. This board dispenses with the eight-phase International Rectifier power-delivery subsystem of many first-generation X299 boards in favor of an all-Intersil 12-phase design, achieved with a six-phase PWM controller run through six doublers. Gigabyte taps the company's ISL99227B integrated power stages for the dirty work and an ISL69138 PWM controller to give those phases their marching orders. Each ISL99227 is rated for 60 A of current and has an exposed thermal pad on both the top and bottom of its package. That exposed metal allows for better cooling through both the heatsink above and the PCB below.
Unlike the somewhat ornamental VRM cooling systems that appeared on many first-generation X299 boards, the Designare EX puts some real heavy metal atop its power-delivery subsystem. The massive heatsink on those Intersil power stages has a beefy metal base capped with chunky fin-like structures. These cut-outs and ridges don't have quite as much surface area as the true fin-stack heatsinks that Gigabyte has begun using on its latest high-end AMD motherboards, but they're a far sight better than the abstract sculptures that tended to cool quite poorly on early X299 products.
The X299 Designare EX gets another lift in VRM cooling from a 30-mm fan attached to the back of the secondary VRM heatsink. This fan draws air through a mesh cutout on the board's integrated I/O shield and exhausts it toward the first memory slot. We're not usually fans of putting such tiny fans in PCs, but Gigabyte has proven judicious in its selection of VRM-cooling spinners every time we've seen one, and the X299 Designare EX is no exception. This fan has proven barely audible in the course of our testing with this board.
Flip the board around, and you'll find a Designare-branded full-coverage backplate. These plates make it less likely that you'll zap sensitive components while handling the board and add some extra backbone against heavy graphics cards and CPU coolers. Unlike the implementation we recently saw on the X399 Aorus Xtreme, the Designare EX's backplate isn't coupled to its VRM-cooling solution by way of thermal pads.
The X299 Designare EX taps Skylake-X CPUs' quad-channel memory controllers with the expected eight memory slots, capable of handling up to 128 GB of RAM. Thanks to Intel's segmentation decisions, however, the board doesn't come with ECC memory support, and its 128-GB capacity is a hard cap, not a suggestion.