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

lokedhs
Member
Registered: 2019-06-06
Posts: 2

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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