Worked great, almost perfect, right out of the box.
So, i bought the z390 motherboard right out of the gate, before even intel's 9th gen cpu's were released, and knowing that asrock had only the initial bios released (which is almost never what you want to run). Fortunately by the time i was able to actually get my hands on an i7-9700k, they had rev'd the taichi ultimate bios a couple times (i should note that even before i flashed it the original seemed to work fine) the board had no problem xmp'ing my corsair lpx 32gb dram 3000mhz c15 memory kit, which i would whole hardheartedly recommend, and i was able to install windows 10 to my intel optane 905p u.2 drive (with m.2 adapter cable) with absolutely no adjustments or special effort. I do notice that the 1.4 bios release, which seems to be better calibrated in some respects, never boosts beyond an all-core 4.6ghz, unless you enable mce (multi-core enhancement). Of course the mce may boost or force you to run beyond what you want from a cooling/noise perspective. I expect they may do better in future bios releases. As well i wasn't impressed with the fan-tastic fan tuning and control adjustments....They need to simplify that and make it work more reliably. I suspect i might update this review to 5 stars after i've used the product a little longer. Right now the overall machine i chose to build around the taichi ultimate is at least twice as fast in every respect and produces half as much noise as my previous i7-3770k / gtx 980. I'm using a corasair hydro 360mm aio which, while not the absolute leader in terms of cooling performance, still does an outstanding job and runs silent (consistent with it's design priority). At idle or just web browsing or using lightweight windows apps, the cpu idles at 28c to 30c and the rtx 2080 (2.75 slot, massive heat sink) runs 40c to 43c...At those temperatures the fans never even kick in on either the aio or the rtx, resulting in an absolutely silent machine until i play games. I built all of this into a roomy (but not too large) define r6 with a single 140mm exhaust, a single 140mm bottom-mounted intake, and of course the 360mm front-mounted aio which as well acts as intake...Albeit with very little draw due to their silent, static-pressure design and the fact that they rarely need to spin up to very high rpm's. Note that the motherboard wants another 4 pin power plug in addition to the traditional 24+8 power connectors. This is a natural consequence of today's motherboards supporting usb 3.1, water pumps, m.2 drives, 8-core cpu's, integrated wifi, and so many other features that didn't even exist a decade ago (not to mention an integrated 10gig nic on the z390 taichi ultimate). Most 750w or larger modular power supplies will come with an additional 4-pin cable, but vendors omit such an extra cable on their 650w or smaller products, which is a shame because 650 watts is plenty (even ideal) for this board, even if populated with a 9th gen cpu and an rtx 2080. Altogether that will never put you over 500w unless you do serious overclocking, and will leave you in the 400-500w "sweet spot" for efficiency when using a 650w supply.