Z390 Taichi Ultimate - High Speed Ram Issues

darkshado wrote: Did you ever find a solution for this? I have 4 x 4133 and they only boot up at 2133 - never into the XMP profile.

Did you check the Asrock approved ram list to make sure your exact model of ram is on it ? Does it say you can run 4 of those DIMMS ?
https://www.asrock.com/MB/Intel/Z390%20Taichi%20Ultimate/index.asp#Memory
There is no 4133 ram on the list that shows 4 dimms (under Dimm Socket support showing 2/4). Only one at 4000 shows as 2/4 Dimms and that is Corsair 4000 CMK32GX4M4K4000C19. There are many at 3600 that show 2/4 dimms so that is probably the best you will ever get from your ram but will have to manually set it, which is also what the OP mentioned he was able to get.

Hi all,

Went through around a dozen pages of post and didn't see a topic that seemed similar enough to post in so i'm creating my own post.

Have two similar builds with the Z390 Taichi Ultimate updated to latest 1.8 bios, both running I9-9900K. All DIMMS have passed four passes of memtest while at JEDEC/2133mhz.

One build has TWO 16GB (2x8GB) kits of GSkill TridentZ 4266 C19, which I verified have sequential serial numbers.

The other build has a 64GB kit (4*16GB) of GSkill TridentZ 3600 C17.

The issue i'm having is neither build will post with memory at XMP profiles. I've tried manually setting the primary timings in bios, increasing ram voltage to 4.1v, and tried VCCSA and VCCIO at up to 1.4V. Voltages and manual timings have had zero effect from what I can tell so i've left everything at auto.

While all settings were set to Auto:
I was able to boot the full 32GB of 4266 memory at 3600mhz.
I was able to boot the 4266 kit with only two dimms in A2/B2 slots at 4000mhz.
I was able to boot the full 64GB 3600 kit on the other build at 3300mhz.

I'm wondering if there are any bios settings that would help me get these speeds up, or if a bios update may improve support for these speeds, or if its simply a limitation of the board and a Maximus or Aorus board would have been better for these mem speeds. Hoping to receive some community or ASRock input as i'm quite fond of the board but its frustrating to not be able to run the memory at rated speed.

As a side note, the speeds I was able to boot at in Auto were the highest speeds that would post and do not seem to be very stable. Have not run memtest or any stress-testing at those speeds to verify stability, but overall i'm not getting close to rated with any stability thusfar.

Thanks!