League of Legends FPS drops over time on good PC (RTX 4070 Ti Super + Ryzen 9 3950X)

[Arni]

Hi everyone,

I'm trying to solve a very strange performance issue in League of Legends. I've already spent many hours troubleshooting and would really appreciate any expert advice.

System:
-Ryzen 9 3950X (all-core 4.2 GHz, stable)
-RTX 4070 Ti Super
-32 GB DDR4 (4x8 GB, XMP enabled)
-Gigabyte B550 Gaming X (BIOS F19h - latest)
-Latest AMD chipset drivers
-NVIDIA driver 610.62 (also tested clean installs using DDU)
-Fresh Windows 11 installation (official Microsoft ISO)
-Fresh LoL installation

Problem:

Problem

At the beginning of a match I get around 230-250 FPS, but during the game my FPS continuously decrease until they reach 110-130 FPS after about 20-30 minutes.

The strange part is that neither the CPU nor the GPU appear to be fully utilized.

My goal is also to stream League of Legends while playing, but I first want to solve this FPS issue. The problem occurs regardless of whether OBS is running or completely closed. Streaming has no measurable impact on the FPS drops.

Observations:
GPU usage often drops to 13-16%
CPU usage stays around 20%
GPU temperatures are low (~55°C)
CPU temperatures are low (~57°C)
GPU clock remains around 2655 MHz
CPU all-core clock remains around 4.2 GHz
One CPU thread reaches 100% load, while overall CPU usage stays low.

CapFrameX results:
GPU is never GPU limited ("Time in GPU load limit = 0%")
GPU load averages only 13-16%
CPU max thread load averages around 81-84%, with peaks at 100%
Frame times become worse as the match progresses.
Things I already tried
Fresh Windows installation
Fresh LoL installation
Clean NVIDIA driver installation with DDU
Latest AMD chipset drivers
Latest BIOS
XMP enabled
High Performance power plan
Disabled GeForce Experience overlay
Removed RGB software
Forced maximum GPU clocks
FPS cap (doesn't help; FPS still gradually decrease)
Temperatures are completely normal
RAM usage is only around 30%
Used Process Lasso to restrict League of Legends to a single CCD (split CPU affinity between CCD0 and CCD1). There was no noticeable improvement.

Additional information:

In a Custom Game, FPS only drop from about 240 to 200 after 20 minutes.

In normal PvP matches, FPS drop much further, often to 110-130 FPS.

Riot Vanguard:

I also noticed that vgm.exe (Riot Vanguard) crashes repeatedly.

Windows Reliability Monitor reports:

vgm.exe
BEX64
Exception code: c0000409
StackHash_0000

I'm not sure whether this is related or just a separate issue.

Questions
Has anyone experienced similar FPS degradation over time in LoL?
Could this be related to the Ryzen 3950X dual-CCD architecture or Windows thread scheduling?
Could Riot Vanguard be interfering with performance?
Is there anything else I should test (WPA/WPR traces, Process Lasso, etc.)?

Any help would be greatly appreciated.

[EchoGhost]

It's just the game engine being outdated.

I've been playing LoL for 12 years if I remember correctly (started at season 2), on 4 different specs:

3770k, GTX 760
6700k, GTX 980Ti
13600k, 3080
Now 9800x3d, 5070 Ti.

And honestly, the game never ran well for me. Stutters appear here and there; FPS drops even to freezing in the middle of combat. While I can enjoy stutter-free and smooth gameplay in other titles.

[crack]

Hi everyone,

I'm trying to solve a very strange performance issue in League of Legends. I've already spent many hours troubleshooting and would really appreciate any expert advice.

System:
-Ryzen 9 3950X (all-core 4.2 GHz, stable)
-RTX 4070 Ti Super
-32 GB DDR4 (4x8 GB, XMP enabled)
-Gigabyte B550 Gaming X (BIOS F19h - latest)
-Latest AMD chipset drivers
-NVIDIA driver 610.62 (also tested clean installs using DDU)
-Fresh Windows 11 installation (official Microsoft ISO)
-Fresh LoL installation

Problem:

Problem

At the beginning of a match I get around 230-250 FPS, but during the game my FPS continuously decrease until they reach 110-130 FPS after about 20-30 minutes.

The strange part is that neither the CPU nor the GPU appear to be fully utilized.

My goal is also to stream League of Legends while playing, but I first want to solve this FPS issue. The problem occurs regardless of whether OBS is running or completely closed. Streaming has no measurable impact on the FPS drops.

Observations:
GPU usage often drops to 13-16%
CPU usage stays around 20%
GPU temperatures are low (~55°C)
CPU temperatures are low (~57°C)
GPU clock remains around 2655 MHz
CPU all-core clock remains around 4.2 GHz
One CPU thread reaches 100% load, while overall CPU usage stays low.

CapFrameX results:
GPU is never GPU limited ("Time in GPU load limit = 0%")
GPU load averages only 13-16%
CPU max thread load averages around 81-84%, with peaks at 100%
Frame times become worse as the match progresses.
Things I already tried
Fresh Windows installation
Fresh LoL installation
Clean NVIDIA driver installation with DDU
Latest AMD chipset drivers
Latest BIOS
XMP enabled
High Performance power plan
Disabled GeForce Experience overlay
Removed RGB software
Forced maximum GPU clocks
FPS cap (doesn't help; FPS still gradually decrease)
Temperatures are completely normal
RAM usage is only around 30%
Used Process Lasso to restrict League of Legends to a single CCD (split CPU affinity between CCD0 and CCD1). There was no noticeable improvement.

Additional information:

In a Custom Game, FPS only drop from about 240 to 200 after 20 minutes.

In normal PvP matches, FPS drop much further, often to 110-130 FPS.

Riot Vanguard:

I also noticed that vgm.exe (Riot Vanguard) crashes repeatedly.

Windows Reliability Monitor reports:

vgm.exe
BEX64
Exception code: c0000409
StackHash_0000

I'm not sure whether this is related or just a separate issue.

Questions
Has anyone experienced similar FPS degradation over time in LoL?
Could this be related to the Ryzen 3950X dual-CCD architecture or Windows thread scheduling?
Could Riot Vanguard be interfering with performance?
Is there anything else I should test (WPA/WPR traces, Process Lasso, etc.)?

Any help would be greatly appreciated.

I have ran this game months ago on a 5600x and RX 7900XT, ran flawlessly *with* an ingame
240 FPS cap, otherwise you get guaranteed annoying stuttering, not really FPS degradation over ingame time elapsing.

The dual ccds and win thread scheduling have nothing to do with this

Vanguard is a piece of shit anticheat spyware that shouldn't exist, it could be the reason your performance sucks.

I guess you could try 3 or 2 sticks? 4 sticks is really pushing it for your mobo with XMP.

The post 566.36 NVIDIA drivers are a gamble in terms of stable performance, it could also be another reason.