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Benchmark Results and Final Analysis
Though automatic-overclocking hasn’t been a problem for any tested board with the Core i9-9900K installed, we remind readers that we’ve always disabled that setting whenever it’s found. And because we also found that some boards re-enabled it whenever XMP memory mode was enabled, we run our basic benchmark set with XMP disabled. For our memory, that means it’s running at DDR4-2400, except during our overclocking evaluation.
Synthetic Benchmarks
There’s very little room to score a synthetic benchmark victory when overclocking is disabled, though both MSI boards in our comparison charts somehow lead the graphics score of our 3DMark Firestrike test. Moreover, the Z390 Extreme4 bombs the PCMark Creative Test, and the voltage regulator thermal throttling we noticed in our power test would be the most-likely cause.
3D Games
The Z390 Extreme4 takes marginal victories at our lowest Ashes and highest F1 2015 test settings, and is close to average in overall gaming performance.
Timed Benchmarks
How does a board go about losing our MS Word and Excel benchmarks? We find it a little hard to believe that these could be strenuous enough to cause voltage regulator thermal throttling, but the benchmarks indicate that some type of throttling has occurred.
Power, Heat, & Efficiency
Something we noticed right away with the Z390 Extreme4 was that it drew much more power than it should, and CPU-Z shows that CPU core voltage is way up at approximately 1.32V. That could easily increase voltage regulator temperatures enough to hasten its thermal limit.
Indeed, voltage regulator temperatures were terrible, and these are just the temps we measured before throttling kicked down the CPU frequency. Meanwhile, the directly-competing MSI MAG Z390 Tomahawk reached its thermal limit and throttled before we could even get an accurate measurement. It appears this ASRock board isn't alone in its issues with the i9-9900K.
That said, while both boards throttled under the stress of a fully-loaded Core i9-9900K, the MAG Z390 Tomahawk appears to have done it with more finesse, helping the board achieve a full two-percent performance lead in the average of benchmarks. Combining the Z390 Extreme4’s performance loss with its terrible power consumption leads us to an 18.3-percent below-average efficiency rating, though that percentage is based on every Z390 board we’ve tested and not just the four in the chart.
Overclocking
Simply putting the Core i9-9900K’s stock 8-core-loaded Intel Turbo Boost ratio in the Overclocking chart would be too generous for the Z390 Extreme4, given that it couldn’t hold that frequency. The MAG Z390 Tomahawk could, but only after we undervolted our CPU.
The Z390 Extreme4 did reach a solid memory overclock however, and it even posted an impressive 42GBps memory bandwidth after doing so. That’s the best we’ve seen from our Core i9-9900K and Kingston DDR4-2933 combo.
Final Thoughts
Perhaps we were too quick to give the formerly-tested MSI MAG Z390 Tomahawk a 2.5/5 in our previous review, given that its low price could put it below the consideration of most Core i9-9900K buyers. But the point was that we expected a board that supports the processor to do so continuously at stock frequencies. Overclocking headroom for such an expensive CPU could be a luxury that most of its buyers wouldn’t pay for. And that brings us to today’s Z390 Extreme4.
The problem for ASRock is that its low price is matched by MSI. Meanwhile, the MSI board held our CPU closer to its rated performance level than the Z390 Extreme4. The ASRock board has the distinct advantage of supporting SLI, but at this price it’s only likely to matter to builders who happen to be carrying over a pair of cards from a previous build. MSI has enticing features of its own, like dual Gigabit Ethernet.
To be fair, ASRock's mid-priced Z390 Xtreme4 isn't the only board we've tested that doesn't properly support the Core i9-9900K. And while we can't say for certain since we didn't test for it, this board should handle lesser CPUs in Intel's mainstream lineup just fine. But the Extrem4 falls down in both performance and power measurements against similarly priced competition. That makes this ASRock model tough to recommend, unless perhaps you are planning to pair it with a lesser CPU and you value SLI and memory overclocking support over what MSI brings to the mid-range table with its MAG Z390 Tomahawk.
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