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#1 2019-09-10 09:03:37

lokedhs
Member
Registered: 2019-06-06
Posts: 3

Thinkpad T490, CPU downclocks after BIOS update

Hardware: Thinkpad T490, 24 GB RAM.

I had a working setup with Bumblebee that allowed me to play games such as Minecraft or Bordelands 2. This worked fine as of last month.

Since then I have done regular software updates as well as an upgrade of the BIOS to version 1.52. I cannot guarantee that the issues I face are caused by the BIOS updated, but it definitely looks like it.

What I noticed was that when starting Minecraft, the framerates are good for a few seconds, until it drops to single digits. It then recovers after a seconds and the cycle repeats.

I started i7z to display the CPU frequency and I noticed that the slowdowns in the game exactly matches the CPU being downclocked to 400 MHz. Once I stop the game, the the CPU speed goes back to normal. It looks very much like what you'd see if the CPU was overheating.

The BIOS is suspected because immediately after upgrading it, I get the following error displayed just after the kernel has started. This message is right before the prompt for the hard disk password, which means at this time no services are actually running, so I think the message is in error, and it would explain why it so eagerly downclocks the CPU:

[    1.060327] mce: CPU4: Package temperature above threshold, cpu clock throttled (total events = 1)

This message is repeated several times for different cpus.

These warnings are displayed before even systemd was loaded, so it's not doing much at this time that would warrant a temperature warning.

It's possible that the message during boot is not relevant, but since the slowdown seen while using the systems looks remarkably similar to thermal throttling, it seems related. Note, however, that I don't see any throttling warnings in dmesg when the problem occurs.

What should I look at in order to fix this? Or is this simply a problem of a too new BIOS version on my machine?

Last edited by lokedhs (2019-09-10 09:03:51)

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#2 2019-09-19 02:32:24

lokedhs
Member
Registered: 2019-06-06
Posts: 3

Re: Thinkpad T490, CPU downclocks after BIOS update

I have found a workaround. Installing throttled fixes the downclocking problem, but using it in conjunction with the performance governor makes the laptop incredibly hot. Is there any risk of damage to the computer if I use this?

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#3 2019-09-19 07:31:43

V1del
Forum Moderator
Registered: 2012-10-16
Posts: 7,608

Re: Thinkpad T490, CPU downclocks after BIOS update

Depends on how hot "hot" is. Check sensors output. It might be that the BIOS is simply very overeager or maybe they've identified actual issues and are thus throttling sooner, in which case you will likely harm the longevity of your CPU.

Last edited by V1del (2019-09-19 07:37:26)

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#4 2019-09-28 22:19:10

boogy
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From: /dev/random
Registered: 2010-05-20
Posts: 30
Website

Re: Thinkpad T490, CPU downclocks after BIOS update

lokedhs wrote:

I have found a workaround. Installing throttled fixes the downclocking problem, but using it in conjunction with the performance governor makes the laptop incredibly hot. Is there any risk of damage to the computer if I use this?

I also have the T490 and had the same errors in dmesg. I've installed the throttled and it seems the errors are less present, but I do see them sometimes. But can you please tel me if you also have problems with the fan noise ? With less than 10% cpu the temperature is around 55°C - 60°C. Which I dont think is normal (correct me if I'm wrong!). And yes I've installed thinkfan to manage the fan and that helped a little bit with the noise. But I dont think the fan and temperature should be so high with very low activity like surfing the web (just chromium and terminal open).


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#5 2019-09-29 13:00:33

boogy
Member
From: /dev/random
Registered: 2010-05-20
Posts: 30
Website

Re: Thinkpad T490, CPU downclocks after BIOS update

After some testing, I've managed to set the NVIDIA card in P8 state as consume as less power as possible. This also makes the CPU much coller I think and the fan less noisy. As described in this reddit post on Fix battery life with nvidia GPU MX250 on Lenovo T490.

Using this hack it was possible to go from 11.5W, 12W down to 7.0W on idle. This allows for a battery life from 4h upto 5h-6h with light-normal usage.

As described in the reddit post, you need to the following:

  • install NVIDIA drivers if not already installed (I don't have bbswitch or optimus installed either)

  • create the below file with the following option:

    cat /etc/modprobe.d/zz-nvidia-modeset.conf
    NVreg_RegistryDwords="OverrideMaxPerf=0x1"
  • install tlp and exclude the nvidia driver

Don't forget to remove any blacklisting of the nvidia driver.
May be this is also important so here are my boot parameters I'm using with systemd-boot:

quiet rw net.ifnames=0 transparent_hugepage=never resume=/dev/mapper/root resume_offset=358400 intel_iommu=on i915.modeset=1 rd.driver.blacklist=nouveau nouveau.modeset=0 nvidia-drm.modeset=0 acpi_oci=! acpi_osi='!Windows 2013' acpi_osi=Linux

I hope this helps other with the same issues regarding battery life and also fan noise on Lenovo ThinkPad T490.


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