Need Help Tuning MCLK/UCLK on My 9800X3D with 6600MHz RAM

KeldoRx · April 16

Hey guys, I'm trying to find out how MCLK AND UCLK work. I have a 9800x3d with 2x32GB Corsair Dominator 6600mhz RAM, and I noticed MCLK is running 3300, but UCLK is running 1650. I read somewhere I lost performance. So when I went to bios, I sent it 1:1, but the PC wouldn't boot. I lowered the RAM to 6000, and now I see 1:1 MCLK 3000 and UCLK 3000 with FCLK 2000. What's the best setting with a 9800x3d? MB X870E Pro ICE and the RAM are CMP64GX5M2X6600C32. Is there a way to run it 1:1 at 6600, or should I tune it down to 6000 or 6200 to get 1:1? Thanks! (Which would perform better for gaming)

RONOTHAN## · April 16

20 minutes ago, KeldoRx said:

Is there a way to run it 1:1 at 6600

If you're really lucky, sometimes, but for most CPUs out there that's a pipedream. Try manually setting the SOC voltage to 1.3V to see if that makes any difference, though realistically if it won't even boot on auto, it won't be stable even at 1.3V (max safe voltage).

21 minutes ago, KeldoRx said:

should I tune it down to 6000 or 6200 to get 1:1?

Yes, you want 1:1 mode for best performance, and sacrificing clock speed is worth it to get that until you get to speeds like 8000. Most chips should do 6400MT/s in 1:1 mode if you want to give that a shot, again you might need to manually set the SOC voltage to 1.3V to get it to work, but there aren't too many chips out there that can't do 6400 (they exist, but with Ryzen 9000 they should be in the minority).

KeldoRx · April 16

20 minutes ago, RONOTHAN## said:

If you're really lucky, sometimes, but for most CPUs out there that's a pipedream. Try manually setting the SOC voltage to 1.3V to see if that makes any difference, though realistically if it won't even boot on auto, it won't be stable even at 1.3V (max safe voltage).

Yes, you want 1:1 mode for best performance, and sacrificing clock speed is worth it to get that until you get to speeds like 8000. Most chips should do 6400MT/s in 1:1 mode if you want to give that a shot, again you might need to manually set the SOC voltage to 1.3V to get it to work, but there aren't too many chips out there that can't do 6400 (they exist, but with Ryzen 9000 they should be in the minority).

I went to bios, set VSOC to 1.3, set speeds to 6400mhz, turned on 1:1, and loaded Windows fine. I'm kind of scared to put it at 6600 at 1.3 because if I do and it doesn't boot, I'll have to clear CMOS again. Question how do I check if 6400mhz is stable, running MCLK 3200 with UCLK 3200? Also, is FCLK running at 2000 fine? Thank you!

RONOTHAN## · April 16

5 minutes ago, KeldoRx said:

I'm kind of scared to put it at 6600 at 1.3 because if I do and it doesn't boot, I'll have to clear CMOS again.

To be fair, clearing CMOS isn't dangerous or anything, it's just a little annoying. After you've done enough memory tuning, doing it is like second nature and really isn't that big a deal.

6 minutes ago, KeldoRx said:

how do I check if 6400mhz is stable, running MCLK 3200 with UCLK 3200?

I've had the best luck with Y-Cruncher running the VT3 stress test, though I'd also want to run a generic memory stress test as well like TestMem5 (I've had the best luck with the 1usmus preset, though different people swear by different tests).

7 minutes ago, KeldoRx said:

Also, is FCLK running at 2000 fine?

Yeah, it's OK. You can probably push it to something like 2133MHz without much issue if you want to for a bit extra performance, though this I would also want to stress test. If you do it, the stress test is the same as the frequency itself, VT3 for a bit of time, though the difference is to play music in the background and listen for weird cutouts since when the FCLK is unstable, it causes system microstutters rather than outright crashes and therefore the way to catch it is with listening for those microstutters.