The first thing which is immediately apparent after removing the PRIME X299-A from its packaging is the exciting new design to which ASUS has chosen to use. Opting for a mint/white colour scheme is a new approach for the company and indeed for any other brand across the motherboard manufacturers, such a theme will clearly offer an alternative to the lack-lustre neutral styling which is rampant at the moment.

The PRIME X299-A looks stunning and is among the most attractive X299 motherboards we’ve seen so far – it also conforms to the standard ATX Form factor, allowing it to fit into vast majority of mid-tower cases.


Since we are dealing with X299 – the PRIME X299-A uses socket LGA 2066, carrying support for the new Kaby Lake-X and Skylake-X processors. While you will need a new HEDT CPU for this motherboard, current coolers supporting LGA 2011 will actually fix into place without any problems as the mounting holes in the corners of the socket are the same diameter.

Covering the VRMs at the top of the motherboard, ASUS has installed a single, silver heatsink which also conceals the 8-phase design; this utilises Digi+ and we have 10K black solid caps used throughout too. Behind the VRMs there is an 8+4pin connector for CPU power delivery and there are two CPU fan headers located at the top also, along with a 12V RGB LED header for case lighting.

For memory, there are eight slots which support quad-channel DDR4 – supporting up to 128GB and 4000MHz. To take advantage of the full-quad channel arrangement and that 128GB you will need a Skylake-X CPU – Kaby Lake-X only supports dual channel. ASUS include a MemOK! Button which is a long-standing feature found on their motherboards, assisting with troublesome memory compatibility issues.

Immediately next to the 24-pin ATX connector there is a PCIE 3.0 x4 M.2 slot, due to the nature of this slot, the drive will stand in a vertical orientation rather than sitting flush to the motherboard. Mounting screws/attachments are provided for a more secure fitment.



Over in the SATA area there is a single USB 3.0 header along with a USB 3.1 Gen2 header for front panel connectivity.

Storage on the PRIME X299-A is largely made up of SATA-based options with up to eight SATA III 6GB/s ports. Along with the upwards facing M.2 slot, ASUS also include a horizontal slot which is found on the underside of the heatsink – which also marries up to the X299 chipset heatsink. This M.2 is once again PCIE 3.0 x4 and capable of delivering up to 32GB/s.


Casting an eye over the PCI Express region there is quite an assortment of different slots available. The configuration is as follows:

34-Lane CPU-
3 x PCIe 3.0/2.0 x16 (x16, x16/x16, x16/x16/x8)
2 x PCIe 3.0 x4 (max at x4 mode) *1
1 x PCIe 3.0/2.0 x1 *3
28-Lane CPU-
3 x PCIe 3.0/2.0 x16 (x16, x16/x8, x16/x8/x1) *4
2 x PCIe 3.0 x4 (max at x4 mode) *1
1 x PCIe 3.0/2.0 x1 *3
16-Lane CPU-
3 x PCIe 3.0/2.0 x16 (x16, x8/x8, x8/x8/x1) *4
2 x PCIe 3.0 x4 (max at x4 mode) *1
1 x PCIe 3.0/2.0 x1 *3
1 x PCIe 3.0/2.0 x1 (x1 mode)

NVIDIA’s SLI and AMD’s CrossFireX technology are both compatible on this motherboard for those wanting to add in more than one graphics card.

Underneath the PCIE slots there is an RGB header for adding LED strips to your computer chassis – this header is designed to work in conjunction with ASUS Aura software. We also have LED debug and an onboard power button for users who might have this configuration on a test bench.

Immediately next to the PCIE slots we have the audio solution which takes the form of ASUS’ Crystal Sound. The codec being used is the Realtek ALC 1220 – providing us with 8-channel high definition audio. ASUS also include a few other additional features to solidify the package – premium Japanese solid CAPs, de-pop circuit, EMI shielding and separated layers for left/right tracks.


Turning to the rear IO panel on the PRIME X299-A, we have a selection of ports that we can take advantage of. The ports available here are as follows:

• USB BIOS Flashback button
• 2x USB 2.0 ports
• 4x USB 3.1 Gen1 ports (Blue)
• 1x Gigabit LAN (via Intel i219V)
• 2x USB 3.1 Gen2 ports – Type A and C (Green)
• Audio jacks including Optical S/PDIF Out