Since many traditional chipset functions now reside on the CPU die and there's only a handful of third-party peripheral controllers out there these days, we rarely see meaningful performance differences between motherboards anymore. That said, we still test system performance when we review motherboards to ensure everything is functioning correctly.
When it comes to testing motherboard performance, we've usually gathered benchmark results using the CPU's peak stock memory multipliers. Since DDR4 is so new, however, and Skylake's 2133MHz maximum stock DDR4 speed is so conservative, we've continued a practice we began with our X99 reviews. We test our Z170 boards with the memory clocked at the highest XMP profile speed we can attain while keeping the CPU at its stock clocks.
We tested the Maximus VIII Impact against Asus' own Z170-A, Gigabyte's Z170X-Gaming 7 and Z170X-Gaming G1, and MSI's Z170A Gaming M5. All the boards were able to keep our DDR4 DIMMs clocking along at 3000 MT/s while maintaining stock CPU clocks, so the results below were gathered with these settings.
When we power on the Impact, it boots slower than the speediest contender by over six seconds. Modern systems have perfectly functional sleep and hibernate modes that can mitigate these boot times, though, so we don't think the lengthy boot time is anything to worry about.
While one's choice of motherboard might not affect performance much, it can have a notable impact on power consumption. We measured total system power draw (sans monitor and speakers) at the wall socket for five minutes of idle time at the Windows desktop. We then repeated the test under a full load of Cinebench rendering with the Unigine Valley demo running at the same time.
The Maximus VIII Impact has the lowest power consumption under load, but it ends up in the middle of the pack under idle conditions. The most interesting result is that under load, the Impact manages to shave off 7W of power when Asus' EPU power-saving feature is enabled. This is a larger power savings than we've seen from previous Asus boards, including the Z170-A.
The following page is loaded with detailed motherboard specifications, system configurations, and test procedures. If you're having trouble getting to sleep—or you just really love tables filled with data—feel free to peruse. For those who jump straight to the conclusion, my lips are sealed.