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Storage, audio, and the goodies
The X99-A II's SATA-based storage connectivity can be found running up the right-hand side of the board. All of the ports are right-angled to face the edge of the board, which can make for easier cable insertion when longer graphics cards are installed.

Here we can see one of the X99 platform's trademarks. The X99A-II has an abundance of SATA-based storage with ten 6Gbps SATA ports in total. Within the gray SATA Express connector are two standard Serial ATA ports atop a backward-compatible SATA Express port. The four SATA ports in the center and the two on the right edge of the picture above—those clad in gray—can be combined into RAID arrays using Intel's drivers. The leftmost four SATA ports, clad in black and labeled SATA6G 7-10, operate in either IDE or AHCI mode only. This arrangement is a fundamental limitation of the X99 chipset. That said, it doesn't preclude you from using OS-managed or third-party software RAID if you'd like.

Hanging out to the left of all the SATA-based storage, we can see a right-angled U.2 connector. Four Gen3 lanes from the processor are shared between this U.2 connector and the M.2 port just behind it. As as result, it's not possible to use both the U.2 and the M.2 connectors at the same time.

The X99-A II's M.2 port is located south of the low-profile chipset heatsink. This lets the board support devices up to 110 mm long, and it could allow mini-SSDs installed here to run cooler than on boards with M.2 connectors situated underneath PCIe x16 slots.

The four Gen3 PCIe lanes grant storage devices connected to either port an impressive amount of potential bandwidth—up to 32 Gb/s (4 GB/s). This is bandwidth straight from the processor, as well, so builders need not worry about their next-gen storage getting bottlenecked by the DMI link connecting the chipset to the CPU. SATA-based M.2 devices need not apply on the X99-A II, though. Only PCIe-based NVMe storage devices are supported.

The X99-A II's rear port cluster looks a little Spartan, but it should have most users covered. The first thing one might notice is the button all the way to the left. This is used to kick off the firmware flash procedure when using Asus' USB BIOS Flashback. To use this handy feature, simply put your USB thumb drive loaded with your desired firmware release into the bottom right-most USB 3.0 Type-A port. Then with your computer off, press the button for three seconds, and the board will start the flash procedure. No need to install a supported processor to update the firmware. Although it might not be used every day, USB BIOS Flashback can come in very handy if you need to flash the firmware to support your processor of choice—not an inconsequential consideration with Broadwell-E.

The remaining three blue USB 3.0 ports are connected to an ASMedia ASM1074 USB 3.0 hub chip, which is fed from one of the X99 chipset's USB 3.0 ports. For USB 3.0 ports directly linked to the chipset, you'll need to look toward the port that can be used for USB BIOS Flashback, or one of the four ports that are made available through two USB 3.0 internal headers.

For the latest USB 3.1 hotness, Asus outfits the X99-A II with both a Type A and a Type C port, courtesy of an ASMedia ASM1142 controller. This controller is connected to two Gen2 PCIe lanes from the chipset. As mentioned on the previous page, these two lanes are also shared with the second x16 PCIe slot. Rounding out the board's USB support, we have four USB 2.0 ports on the rear port cluster, with four more available via two internal headers.

A single PS/2 port capable of supporting either a keyboard or a mouse is the only legacy interface to be found on the port cluster. This port, along with the serial port header found on the bottom of the board come thanks to the X99-A II's Super I/O controller, a Nuvoton NCT6791D.

The Gigabit Ethernet port is powered by Intel's I218-V controller. Asus bundles its own traffic prioritization software with the X99-A II, called Turbo LAN. This utility aims to improve ping times when online games are competing with other applications for bandwidth. While packet prioritization is nice in theory, it doesn't help if the network congestion is occurring at some point outside of the PC.

After all those words, here's a colorful diagram to show diagram to tie it all together:

The X99-A II's onboard audio implementation goes under Asus' "Crystal Sound 3" moniker. The actual hardware underneath is the familiar ALC1150 codec from Realtek, backed by a TI R4580 amplifier and high-end Nichicon audio capacitors.

Asus' audio hardware choices have given the X99-A II a good foundation. But, that's only half the picture. Those sensitive analog audio signals still have to make their way to the rear cluster audio outputs. Thankfully, Asus has taken measures to keep these signals as noise-free as possible. A pre-regulator is placed in front of the audio codec to minimize power supply noise. Left and right output channels are split between different PCB layers. Shielding is applied to both the codec and the analog traces. The TI amplifier chip's output can be routed to either the front or rear outputs in software. A special "de-pop" circuit should prevent popping noises through speakers and headphones during startup.

The X99-A II's analog audio output produces sound that made my ears happy. I didn't notice any untoward noise under a variety of load and idle conditions. For those who want digital output from the board, DTS Connect can encode multi-channel digital output in real time. Another DTS component, Studio Sound, enables surround sound virtualization for stereo speakers and headphones.

This mobo is equipped with a number of builder-friendly features. The first is a CPU installation tool that's actually fairly nifty. Simply pop your processor into the tool, then insert that whole combo into the specially designed insertion point in the socket, lower the CPU down, close the socket latches and you're done. The installation tool remains in the socket with the chip for easy removal. This tool makes it much less scary to mate $1,650 of CPU with the LGA 2011v3 socket.

A front-panel wiring block—Asus calls it a Q-Connector—is included with the board. This makes the finicky job of wiring up these headers so much more pleasant. It sure beats fumbling with a flashlight in a dimly-lit case.

Just above the front-panel header, we can see headers for clearing the CMOS, as well as the DirectKey firmware shortcut. DirectKey offers a convenient way to enter the UEFI by default without having to resort to furious mashing of the Del key.

For those users needing more than five fan headers, the X99-A II fully supports Asus' fan extension card. This extension module connects to the EXT_FAN header shown above, and it provides three more four-pin fan headers and three more connectors for standard temperature probes. Thermistors attached to the fan module supply reference temperatures to the fan control intelligence managed by the board's firmware and utility software.

A high-quality cushioned I/O shield comes with the X99-A II. This not only makes installing the motherboard in a case easier, it also may save your fingers from getting sliced in the process.

In the center of the board, all the way at the bottom is a two-digit diagnostic display that shows debug codes when the system boots. This readout can be handy if you're trying to solve problems that occur very early in the boot process. To the left of this display, we find onboard buttons for power and reset. These can be very handy when operating the board outside of a chassis.

Sandwiched between the serial port header and the onboard buttons is a 4-pin RGB header. LED lighting strips can be connected here to tie them into Asus' Aura lighting system. By default the LEDs glow a bright white in a slow pulsing fashion, but both the color and the nature of the pulsing can be tweaked in both the firmware and Asus' bundled software.

Despite mobo makers getting big into the bling, the X99-A II has a handful of LEDs that serve a higher purpose than impressing your friends. Tucked away between the 24-pin ATX power connector and the DIMM slots are a series of individual LEDs that show the status of key components during the boot process: CPU, memory, GPU, and boot device. If an issue is encountered with one of these devices during boot, its LED will stay lit. While this is somewhat superfluous given the board's two-digit display, these LEDs can provide an immediate diagnosis without having to open up the user manual to look up boot codes.

One last handy feature to touch on is Asus' MemOK! button. Should the board be populated with unsupported RAM, pressing the MemOK! button next to the DIMM slots will make the board automatically cycle through memory profiles until it finds one that works.

Having reached the end of the hardware portion of the X99-A II tour, now is a good time to visit the restroom, stretch your legs, and grab a snack before we dive into the the board's softer side.