MSI X299 Gaming Pro Carbon AC Motherboard

Intel’s new X299 platform replicates what we’ve seen in its mainstream desktop advancements over the past two years, and the most amazing part of that is the age of the X99 it replaces. HEDT (High-End Desktop) users had to wait all this time for a faster DMI interface to connect various devices through the chipset to the CPU, while suffering with an old one that limited all 10 of their SATA SSDs and any attached network and USB controllers to a combined total of 20Gb/s. At 32Gb/s, even the latest iteration of Thunderbolt was too fast for the X99. So, what does all of this newfangled, mainstream tech add to the high end?

Thanks to the more recent DMI 3.0 interface, the chipset link is exactly as fast as a Thunderbolt 3 controller. Add one and fill it with multiple devices, and you’re still left with your SATA drives fighting for bandwidth. I say that in jest, knowing that most boards will get their M.2, U.2, network, and Thunderbolt 3 bandwidth over that DMI 3.0 x4 link, so that overloading any of those interfaces could make it feel like you’re still stuck on SATA. Of course, the LGA 2066 platform still has the same workaround as the LGA 2011 and 2011-v3: The CPU has up to 44 lanes. Unfortunately, Intel saw fit to add a basic dual-channel-memory CPU with 16 PCI lanes to the mix, in the form of Kaby Lake-X. For those who thought that 28-lane CPUs were stuffing up the X99, Intel decided to double down on those difficulties.

Fortunately, the CPUs are a little faster, for the most part, and the chipset’s link is twice as fast as the previous version, even if twice as fast isn’t enough. You’ve probably read the reviews that show situations where the new cores fall behind Broadwell-E, and I’ll just leave it to developers to work those pieces out as I focus on what motherboard manufacturers have accomplished in their efforts to help Skylake-X motherboards work around Kaby Lake-X restrictions.

We’re running back-to-back reviews of MSI’s X299 Gaming Pro Carbon AC and the Asus Prime X299-Deluxe, but we’re presenting the results of both boards in both reviews, so this is a bit of a spoiler alert. The Asus motherboard review will run later today. But let’s start with MSI.


The X299 Gaming Pro Carbon AC carries the tradition of MSI’s Pro Carbon series by having only a few more than the “belly button” high end features of USB 3.1 Gen 2 and, when it’s in the name, WiFi. The X299 version gets two M.2 slots, because nearly every other enthusiast motherboard has at least that many, plus a U.2 port, a Port 80 diagnostics display, and on-board power and reset buttons to satisfy similar expectations of the enthusiast community. The few additions are the BIOS Flashback+ feature for programing a new BIOS when the CPU model you ordered is newer than the board you received, a Demo button for the LED lighting, and a “Game Boost” knob that selects between 11 overclocking profiles.

That’s not to say we’d expect the Gaming Pro Carbon AC to be priced near the bottom of the enthusiast market though, as MSI does a few things to enhance the “regular” features, such as reinforcing the DIMMs and x16 slots with stainless steel shells, gold plating its audio jacks, adding a revised USB 3.1 Gen2 front-panel connector to the improved ASM3142 USB 3.1 controller, tossing in a couple decorative covers for M.2 drives, and adding gold and silver replacements for its Carbon accent panels. While some of these could be done for spare change, they add to the expense of a high-end Intel 8265 Wi-Fi/Bluetooth module and a special ASIC that enables Flashback+.

Not that most users would want to replace the carbon fiber look with metallic silver or gold paint, but those who do will save some effort and retain MSI’s logos. Scanning around the board for fitment issues, the only conflict between slots and on-board connectors are the bottom SATA ports, which are around 8.5” forward of the rear edge, and could impact certain 3-way SLI configurations, depending on the size and shape of the card’s heat sink. The Game Boost knob also has the potential of getting in the way with its 5/8” height at an 8” distance from the rear edge.

The bottom SATA ports might not be a problem if you plan to add a U.2 drive, since it consumes the same four HSIO resources as SATA ports 5-8. Of course you could add a U.2 adapter to one of the M.2 slots, unless you think of U.2 as existing because motherboard designers run out of space for M.2 slots. And, if you need more U.2 or M.2 drives, that second x16-length slot isn’t designed with graphics cards in mind anyway: Its four lanes are perfect for hosting an M.2 drive, U.2 adapter, or even some other card-mounted drive controller. If you’re now confused about the board’s 3-way SLI capability, it comes via the first, third, and fourth x16-length slots. It goes without saying that CrossFire configurations are not restricted in these ways, but we’ll say it anyway.

Here’s where things get weird: Per MSI documents, the bottom PCIe slot gets its eight lanes from the top slot, and the third slot is locked into eight pathways…unless you’re using a Kaby Lake-X (16-lane) processor. Then, and only then, the second slot can steal four lanes from the third whenever a card is detected there. And Kaby Lake-X also gives up any connectivity whatsoever to the bottom slot. Kaby Lake-X also disables half the DIMMs: The more we consider the limitations of bottom-tier LGA 2066 processors (Core i7-7740X and Core i5-7640X), the more apt we are to recommend Kaby Lake customers stick to less-expensive Z270 motherboards.

The X299 Gaming Pro Carbon AC installation kit includes four SATA cables, a driver and applications disc, an RGB extension cable, two magnetic-base Wi-Fi antennas, an HB-style SLI bridge, several standoffs for mounting 3D-printable accessory covers, a case badge, gold and silver replacements for the carbon-look accents, an I/O shield, full printed documentation, and a sheet of adhesive cable tags.

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