When equipped with the same components running at the same speeds, motherboards typically have little impact on system performance. There are rare exceptions, so we still run a range of application and peripheral tests to look for outliers, but we didn't find any with the X99-A. In most cases, the performance differences between this board and the X99-Deluxe are smaller than the run-to-run variance.
Gigabyte's X99-UD4 also appears in the graphs below. That board's DRAM multipliers only go up to 26.66X, so the UD4 can't run our DDR4-2800 modules at full tilt without also overclocking the CPU. We tested the UD4 at DDR4-2666 speeds to ensure stock CPU clocks, and that handicap was barely evident outside our memory bandwidth benchmark.
Nothing to see here, folks.
We also measured cold boot times, and the X99-A made it to the desktop slightly faster than the other Haswell-E boards we've tested:
Shaving a few seconds off the boot time is nice, but it's hard to get excited about a task that's performed so infrequently. If you really want quick boot times, you're better off with Z97 boards, which typically boot in 13-16 seconds with similar hardware.
Although motherboards have little effect on performance, they can influence power consumption. We measured total system power draw (sans monitor and speakers) at the wall socket over a five-minute idle period and under a load comprising Unigine's Valley graphics benchmark and Cinebench's multi-core CPU rendering test. The Asus boards were tested with and without their EPU power-saving measures enabled.
The X99-A is particularly power-hungry at idle, where it consumes 3W more than its Deluxe sibling and 16W more than the Gigabyte board. The contest is closer under load, but even with its EPU mojo turned on, the X99-A still draws 11W more than our low-power leader.
Asus' LGA2011 boards have a history of higher power draw, so the results aren't terribly surprising, even if they are a little disappointing. At least the deltas are small enough that cooling requirements shouldn't be affected.