UPDATE (December 9th):
I think I might have found the culprit. I got rid of the stutters temporarily by doing this:
Go into BIOS and apply XMP profile 2 (3733MHz CL17) instead of profile 1 (3866MHz CL18). (I actually ended up with 3726.6MHz CL18, though.)
Manually set FCLK to half the memory clock (1866MHz) to achieve the recommended 1:1 ratio.
This morning, however, HWiNFO was showing FCLK constantly fluctuating above the frequency that it's supposed to use (sometimes even reaching 2027 MHz, probably a wrong reading). UCLK was still stable at 1866MHz, though.
I turned on my PC again this evening. Everything is magically back to normal. It would seem that my BIOS occasionally applies wrong FCLK settings on boot. Maybe I need to forget about XMP and tweak the RAM myself.
UPDATE 2:
Sometimes, FCLK starts fluctuating again for no apparent reason after the PC has been running for a while. Turning off the computer, unplugging it from the power socket, and plugging it back in fixes the issue.
UPDATE 3 [FIXED]:
I disabled DF C-States in BIOS and FCLK stopped doing that weird thing. No big stutters anymore but I still get one from time to time.
Original post below.
The issue:
I have a brand new gaming PC that I built myself in October (specs below). On November 10th I installed a BIOS update for my Asus TUF X570-Plus Wi-Fi motherboard (v1404, 2019/11/08).
Two days later (I had not used my PC in the meantime) I started noticing very frequent stutters in all my games: they freeze for a split second approximately every 20 seconds and then instantly go back to their original framerate.
Some games are more affected than others: Rainbow Six Siege shows almost no issues, but Minecraft stutters a lot. Lucky for me, I mostly play Siege.
What I know:
ALL my drivers are up to date (graphics, chipset, LAN, Wi-Fi, audio, etc.)
Windows 10 is up to date.
My system temperatures (CPU, GPU, chipset, etc. are all normal (below 70°C) even under heavy load.
My CPU and GPU loads and frequencies are normal and hit their expected values when running games.
XMP (DOCP for Asus motherboards) correctly applies RAM frequencies and timings (3866MHz CL18).
All my PC's connectors and cables are correctly plugged in.
When recording a benchmark with MSI Afterburner, the 1% low framerate is always around 10-20 FPS (very low indeed, considering that some games average at about 200 FPS).
My GPU (RTX 2070 Super) emits a bit of coil whine (buzzing) when playing games (it's normal and it's always been like that). However, during the micro stutters, the buzzing sound also stops for an instant, as if the GPU actually stopped working during that time.
When I alt-tab out of a game without closing it, the PC sometimes becomes sluggish in general.
If I reboot my PC a few times, the issue goes away and I can play some games normally, but not all games.
Sometimes, my PC takes a very long time to boot (about a minute, instead of the 10 seconds that you could expect from an SSD like mine).
A few times, after rebooting my PC, I've had a black screen with the the motherboard's "DRAM" LED turning on (indicating some kind of memory issue).
Windows Memory Diagnostic does not detect any problem.
Sometimes LatencyMon detects high latency from DirectX Graphics Kernel and from Nvidia Kernel Mode Driver, but it actually seems unrelated to the stutters.
I am getting below-average scores in 3DMark (probably irrelevant).
I noticed that one specific game action always causes a stutter: opening an NPC's items store in SoT (may be unrelated).
What I've tried:
Reset my BIOS settings and re-apply XMP.
Re-download and flash the same BIOS version again (I can't revert back to a previous version).
Reset the CMOS by removing the board's battery.
Reinstall Windows 10 using Windows Media Creation Tool.
Uninstall and reinstall all drivers.
Closing all unnecessary 3rd party processes in the background
Complete disk wipe and clean install of Windows 10 from BIOS using a USB stick. I manually downloaded my programs and games again. I only updated my drivers using my motherboard's utility software (Asus Armoury Crate) and my GPU driver using GeForce Experience. It's not as bad as before now. Waiting for a new BIOS update before I try anything else.
(November 27th) Updated BIOS to v1405. Updated AMD X570 Chipset drivers as well. No difference.
My specs:
CPU: Ryzen 7 3700X
Motherboard: Asus TUF X570-Plus Wi-Fi
RAM: Viper Steel 16GB 3866MHz C18
SSD: Sabrent Rocket 2TB NVMe
HDD: None
GPU: MSI Nvidia GeForce RTX 2070 Super Ventus OC
PSU: Cooler Master MasterWatt 650
Chassis: Cooler Master H500
OS: Windows 10 Pro 1909