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ASRock X99 Extreme6/ac Motherboard Review

Featuring the same wireless controller as its closest competitor, ASRock’s X99 Pro adds a second gigabit Ethernet controller and removes a few pathway sharing issues. Have we finally found a value-winning solution for high-end LGA 2011-v3 buyers?

X99 Extreme6/ac Firmware And Software

Manufacturer-defined overclocks within the X99 Extreme6/ac's firmware include 4GHz at 1.20V core, 4.2GHz at 1.22V, 4.4GHz at 1.31V and 4.5GHz at 1.36V. Those voltage are high enough to stabilize the frequencies, but anything beyond 1.30V often causes thermal throttling on our Haswell-E sample that acts like Turbo Boost…in reverse.

Getting to the usual 44x CPU multiplier with a 1.28V core voltage was easy (as usual), but going from there to a 101MHz BCLK caused the system to crash. We were stuck at 4.4GHz, rather than the expected 4.44GHz.

ASRock doesn’t expose any hidden memory ratios, limiting the X99 Extrem6 to the 10x ratio of less feature-rich boards. That gets enthusiasts a 2666MT/s data rate at the DRAM controller’s 4:3 ratio (1.33x) to the CPU core.

The X99 Extreme6/ac still supports our memory’s DDR4-3000 XMP setting, but only by specifying a 1.25x strap and corresponding 125MHz BCLK. Hiding its over-voltage, our meter showed an actual 1.349V at the 1.330V setting.

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The X99 Extreme6/ac includes a full range of primary, secondary and tertiary timings. A pop-up “DRAM Tweaker” menu provides a list of the memory’s rated settings.

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A 1.282V setting bumped the CPU core over its initial 1.279V at 1.28V.

APP Shop is ASRock’s downloader program, where the “Apps” page is little more than a group of freeware links. Most valuable of these in dollar terms is ASRock Cloud, which is a free year’s subscription to Orbweb ME hosting service.

ASRock A-Tuning includes an auto-tuning algorithm that’s supposed to gradually increase clock speed while cycling stability tests to reach the CPU’s optimal setting. It found 4.37GHz at 1.20V (CPU core) and enabled XMP at 1.38V (memory), but Prime95 crashed after several seconds of running an AVX-optimized multi-core load. Noting that our CPU’s memory controller doesn’t appear to work well at voltage levels in excess of 1.365V, your results may be better.

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Manual configuration is a viable option, with A-Tuning providing Windows-based access to the full range of firmware-level voltage and frequency controls. We were able to confirm that processor voltage, multiplier and platform BCLK are all configurable without rebooting.

Since A-Tuning hasn’t been significantly revised in a long time, other software features remain consistent with our previous X99 Extreme4 review. These include XFast RAM (RAM disk), XFast LAN (packet prioritization by cFOS), FAN-Tastic fan speed tuning, “Dehumidifier” artificial load cycling, USB Key login authentication and the control app for the included HDD Saver hard drive power cable.

Thomas Soderstrom
Thomas Soderstrom is a Senior Staff Editor at Tom's Hardware US. He tests and reviews cases, cooling, memory and motherboards.