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#1 2022-01-14 14:52:47

bnounu
Member
Registered: 2020-09-28
Posts: 3

CPU frequency randomly dropping to 800mhz during games

Hello,

I'm having an issue where games have 2-3 second stutters randomly every ~2 minutes. This happens both on heavy games like GTA V and light games like Terraria. While trying to troubleshoot the issue I discovered that the CPU frequency drops from 3-4GHz to 800MHz during those stutters.

I'm using the XanMod kernel which sets the CPU governor to "performance" by default. I also tried:
- Using the default or LTS kernel.
- Increasing the minimum CPU frequency the governor can set (cpupower frequency-set -d 2000000).
- Selecting another CPU governor.
But nothing stops those random 800MHz drops from happening. The laptop is always on AC power.

Hardware:
- Lenovo Legion 7 15IMHg05
- CPU: Intel i7-10875H

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#2 2022-01-14 15:06:36

mpan
Member
Registered: 2012-08-01
Posts: 750
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Re: CPU frequency randomly dropping to 800mhz during games

What are temperatures just before and during the stutters? Could be throttling due to overheating.


Sometimes I seem a bit harsh — don’t get offended too easily! PGP: 7C848198AE93D3BB

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#3 2022-01-14 20:35:22

bnounu
Member
Registered: 2020-09-28
Posts: 3

Re: CPU frequency randomly dropping to 800mhz during games

mpan wrote:

What are temperatures just before and during the stutters? Could be throttling due to overheating.

Around 90-95C. But it maintains base clock and turbos consistently, so I don't see a reason for it to drop to 800MHz randomly.

I did some tests while monitoring the CPU temp, frequency and power: https://imgur.com/a/Q3f8n13. The temperature dips for a second when the frequency drops, but it bounces right back.

I also discovered a few more things:
- Disabling CPU turbo solves the issue (or at least makes it much more rare) without any noticeable performance loss.
- My laptop has a quiet/balanced/performance setting. The issue happens in quiet and balanced but not in performance. The downside being that it gets very loud, but I also get a nice performance boost.

So I think this is a power budget issue. I generally keep it in on balanced, so probably the firmware tries to keep the CPU power moderate but sometimes it starves it of power and the CPU responds by dropping the frequency hard in order to maintain operation. Disabling turbo solves the issue by reducing CPU power spikes, while the laptop performance mode solves it by increases CPU power budget. This is just speculation, I need to do more testing.

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