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Storage, ports, and the little things
Because the X99 chipset has 10 SATA 6Gbps ports, the X99-A can host a stack of drives without resorting to third-party controllers. There are some associated limitations, though. Only six ports are managed by Intel's Rapid Storage Technology software, which has built-in RAID support. The remaining four (the ones on the left in the picture below) are separate from the RST framework. These second-class citizens work just fine with individual drives, but they can only participate in RAID arrays via third-party software.

Two of the full-fat SATA ports reside inside a slim SATA Express connector. This shared physical interface is tied to a "flex I/O" link in the chipset that can hook into dual SATA drives or one SATAe device. The latter has access to 1GB/s of bandwidth from dual PCIe Gen2 lanes, much like similar flex implementations on Z97 boards.

The X99-A's M.2 slot is part of the storage picture, too, but it bypasses the chipset and hooks into the CPU. Mini SSDs have access to a staggering 4GB/s of bandwidth—enough headroom for not only today's fastest M.2 drives, but also tomorrow's next-gen hotness. The only catch is that the CPU has no clue what to do with SATA-based SSDs, ruling out compatibility with most of the M.2 drives on the market right now. And that's just fine, because PCIe SSDs have a lot more potential. Besides, the X99-A has enough SATA connectivity already.

Both of the X99-A's internal USB 3.0 headers are visible in the image above. Each one is connected to dual ports in the X99 chipset, leaving only two native SuperSpeed ports for the rear cluster pictured below. Asus bolsters those connections with a two-port controller and one-to-four hub, bringing the number of rear-mounted USB 3.0 ports up to six.

PS/2 LAN Audio
1 Gigabit Ethernet via Intel I218-V
8-channel audio via Realtek ALC1150 and amplifier
4 USB 2.0 via X99
2 USB 3.0 via ASMedia ASM1042AE controller
3 USB 3.0 via X99 and ASMedia ASM1074 hub
1 USB 3.0 via X99

The table above illustrates how the various ports are connected. The ports supplied by the ASMedia controller are slower than the other USB 3.0 options, so we wouldn't recommend them for truly high-speed devices. That said, the ASMedia chip still hit 250-260MB/s in our sequential tests, so it's certainly fast enough for mechanical storage.

Intel Gigabit Ethernet? Check.

CMOS reset button? Nope. What looks like a reset switch is actually the trigger for USB Flashback, which can update the motherboard firmware with only a thumb drive and power supply connected. Good guess, though.

On the audio front, Realtek's ALC1150 codec collaborates with Texas Instruments' R4580 amplifier. The amp can be switched between the stereo and front-panel outputs on the fly, and it's joined by the usual assortment of enhancements, including audio-specific capacitors and isolated analog traces. More importantly, the drivers support DTS UltraPC II surround virtualization and DTS Connect multi-channel encoding.

The onboard audio sounds decent to my ears, and the X99-A scores well in RightMark Audio Analyzer, which measures analog signal quality. If you're really serious about audio quality, though, you're better off using the digital output or installing a discrete sound card or USB DAC.

Although they're not terribly exciting, builder-friendly features like the X99-A's cushioned I/O shield and front-panel wiring blocks make system assembly much easier. The shield won't slice your fingers or get caught up in the rear ports, and the blocks simplify front-panel wiring immensely. Both should be standard equipment on all enthusiast-oriented motherboards.

Just behind the port blocks is a series of switches to control features like XMP profiles, EPU power saving, and TPU auto-overclocking. These features can be activated in the firmware, of course, but some folks apparently prefer onboard switches. The X99-A also has physical power and reset buttons, a POST code display, and a DirectKey header that can be used to boot directly into the firmware. Unless you want to short the DirectKey header with a screwdriver, you'll need a momentary switch mechanism (like those used for chassis power and reset buttons) to trigger the boot-to-firmware shortcut.

So ends our tour of the X99-A's hardware, but there's a lot more to this board than what's on the PCB. Next, we'll look at the firmware, the software, and how well this thing overclocks.