53 lines
2.0 KiB
Markdown
53 lines
2.0 KiB
Markdown
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---
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title: Dell Latitude thermal throttling
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x-toc-enable: true
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...
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On some Dell Latitude laptops, you may encounter random shutdowns on
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heavy load. We believe this is because the SMSC EC is overly conservative
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by default; it is in charge of handling thermals and fan control on this
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machine. Our theory is that coreboot needs to write certain EC commands
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to allow higher temperatures; please read:
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<https://codeberg.org/libreboot/lbmk/issues/202>
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Basically, what you need to do is:
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* Use high quality thermal paste (don't use the same dried up paste that the
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laptop came with, if you bought it on ebay for example). Arctic MX-6 is good.
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* Check that the fan works reliably
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Also: the `intel_pstate` driver can be used to artifically cap CPU speed. See:
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<https://www.kernel.org/doc/html/v4.12/admin-guide/pm/intel_pstate.html>
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When you use this machine, it is recommended that you cap the CPU speed once
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you've booted into Linux. Set it to something like 50% at first. Then run a
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stress test, for example:
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stress -c x
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Where `x` is the number of CPU cores, e.g. 2. Monitor the temperatures using
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something like `xsensors`, making sure the CPU doesn't exceed 80c temperature.
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You can also monitor CPU speeds in Linux like so:
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watch -n .2 grep MHz /proc/cpuinfo
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This will let you know what speed you're at. You can use this to determine
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whether the `intel_pstate` driver is working. How to cap speed to 50 percent, as
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in the above example:
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echo 50 > /sys/devices/system/cpu/cpufreq/intel_pstate/max_perf_pct
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Gradually increase the CPU speed (up to 100 on `max_perf_pct`), waiting a few
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minutes each time. You should ensure that your machine does not exceed 80C.
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Dell's thermal safety is far too protective by default, on some of these, and
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we don't yet know how to properly configure it. Running a CPU below 80c in
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temperature and never higher than that, is a good idea anyway, for the
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long term life of your CPU.
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Regardless, thermal shutdown is extremely reliable on this machine, but Dell
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makes it shut down *earlier*, before it can even start to CPU throttle.
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