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Journeyman III

3900xt not boosting properly

Just picked up a brand new 3900XT to replace my 3600X, and I am seeing almost no improvement in single-threaded benchmarks. I'm getting low 2700's in Passmark single-thread CPU, and an absolute max of 506 in R20 single-thread. Also, if I enable PBO in bios, the cpu actually boosts even LOWER than if I just leave it on Auto, and runs single-thread benchmarks considerably slower than my 3600X.

I'm running the latest bios for my motherboard, f20b, that was released this week. I've loaded optimized defaults and started over, I've cleared CMOS from the motherboard jumper, and I've reflashed several times. I have the latest chipset drivers and I am running the Ryzen Performance power profile in Windows 10.

Temperature isn't an issue, I'm running a 240mm AIO watercooler as a case intake, and even in the highest load conditions it doesn't even get to 70C.

Over the weekend I tried a second 3900XT from a different store, and had almost exactly the same results. The CPU runs the fastest in all benchmarks (considerably slower than even a 3900X) with optimized bios defaults loaded. As soon as I enable PBO, it becomes somehow even slower, on par with or slower than a 3600X.

  • Motherboard: Gigabyte x570 AORUS ELITE bios ver. f20b

  • CPU: AMD Ryzen 9 3900XT, 240mm ASUS AIO

  • PSU: Corsair 850W 80+ Platinum

  • System Memory: 32GB Dual Channel 3200 MHz

  • Windows 10 19041.330

2 Replies
Journeyman III

i also have a weird behavior on the 3900XT, first if you look at the CPUID, the 12 cores on idle rarely go up to 46.75x and never to 47x, but ok i  have read that they have an issue about that, It seem to like to run at max 43.5x which is the max you can see on each cores other that the rare and elusive 46.5 who appear and go away as fast as the higgs boson !! But my problem is that when you ask the CPU to work on any test what so ever it only get each core at 4150 and nothing more, I am used to my intel devil canyon who go up to 4.4 as soon as you ask anything and stay there or close to.

On the msi mpg x570 gaming carbon wifi you can put the overclock game mode to add a 350mhz on the 3.8 of the CPU, if you do that all your cores are kind of block to 2150 and never move under load or no load, so i dont use it hoping to get my 4.7 one day but no luck. what's the point to advertise a 4.7 boost if it is not really going there when needed.

I just hope my CPU is broken and i will get a RMA....

Other weird thing is that when i first open the bios before installing windows it was written 4.52ghz, then the next day 4.6 ghz, dont know where it come from because it is a 3.8 or a 4.7 boost but nowhere a 4.52 or a 4.6 !!

Then a installed windows and the bios now write 3.8ghz, so i guess it needed windows to tell him what CPU was on the board !! lol

Anyways tomorrow i will try to wipe everything and start over, i will take picture of the bios and then windows CPUID reading.  on a side note i even have a program forgot about what is was, i think aida65 but anyways, it identified the cpu as and Ryzen 9 3900XT 4300MHZ !! basically the truth really !

MSI MPG X570 GAMING CARBON WIFI  last bios available

RYZEN 9 3900XT


GSKILL 32G DDR4 3200 CL14

still waiting to get my RTX 2070 



If you have a possibility get ride of MSI x570 Carbon wifi motherboard. This motherboard overheat awfully.