Question I need help understanding my PSU's distribution instability.

Sep 10, 2020
I recently built my first gaming PC (specs at the end) after spending 3-4 months slowly educating myself on the ins and outs of PC hardware.

Unfortunately, after three weeks of my PC working gorgeously, I've started to have some serious frame drops in a select few games (Rocket League and Valorant specifically). Other games like Risk of Rain, all my VR games (beat saber, half life alyx), etc, run perfectly fine. Also, the frame drops I am experiencing, only occur after a few minutes inside the game. With the specs of my build, I have absolutely no tolerance for this kind of performance drop after what I payed, and would love your help troubleshooting my issue.

So I devised an experiment, I would log data in GPU-Z and run the game with a stop-watch beside me, and I would time when I would experience frame drops and see if I could correlate those moments to changes in the sensor data from GPU-Z and perhaps locate the cause.

First, my specs:
CPU: i9-9900k
GPU: EVGA 2080 TI XC Ultra
RAM: 16GB DDR4 3200
CPU Cooler: Noctua DH-14
PSU: EVGA 80+ 850W Platinum

The experimental design:
Idle PC for 30s
Launch Rocket League (RL)
Idle in Main menu for 30s
Launch Freeplay in RL
idle in Freeplay for 30s
Begin playing (driving, jumping, boosting, etc) until I experienced the frame drop, then idle for 30s
close RL and idle PC for 60s

Every part of my system looked fine except for one location: the power usage. The drops were not caused by thermal throttling or anything because A) my GPU/CPU never exceeded 75C, and B) RL is not a demanding game, so it could never load my hardware to overheat. Anyways, what I found was quite interesting, and seemed like a smoking gun. See the linked image of my data plot for power usage:


Above is my PC's component power draw [W] as a function of time elapsed [seconds]. Below is a description of the markers in the data plots:
T1 is the moment I launch Rocket League.
T2 is the moment I'm in the main menu, then idle for 30s
T3 is when I launch Freeplay
T4 is when I'm In-game, I then idle (don't put input any commands into my controller) for 30s
T5 is the moment I start 'playing' and give inputs into my game.
After about 30 seconds, at T6, I start to notice big frame drops in my gameplay (from 250hz to 80hz). I then go idle for 30s.
T7 I close RL, and idle for 60 seconds, and end the data logger at T8

From the above data, it's clear that the moment I start giving the game inputs and playing the game the power supply to all the components begins to fluctuate randomly for about 30 seconds before dropping dramatically to a value just above its idle draw, and this big drop in power is what I'm experiencing as a drop in frames per second.

My question is then: What is causing this power instability? Is there anything I can do to remedy this problem, or does it look like my PSU is defective? Lastly, could this data be a red-herring to a different issue that a novice such as myself is not seeing/considering? If so, what data from GPU-Z could I provide to this thread to get a clearer picture of my problem?

Thank you for your time and help.