The X1 Carbon is one of the most popular notebooks for the ambitious Linux user. With the 6th gen, however, there have been a couple of caveats. Some other notebooks of the same family (like the T480s) are affected, as well.

If you’re not running the latest BIOS version (1.30), we strongly recommend upgrading. The most pressing issues under Linux that have been solved since 1.23 are:

ACPI S3 (Sleep/Suspend) doesn’t work (A workaround exists which involves patching the ACPI tables manually)

When using speakers through the audio jack, there was a pretty annoying fizzling sound - unless a certain audio volume was used. So specifically for business users who do a lot of conference calls, this was pretty hard to bear.

You can upgrade your BIOS (without Windows) by following these instructions:

https://github.com/fiji-flo/x1carbon2018s3

https://fwupd.org/lvfs/component/1023/all

There’s one big caveat left even in the latest BIOS version, though. When you’re running a CPU intensive task, your machine will be only about 50% as fast as it could be!

Let that sink in for a moment.

The reason is that under Linux the CPU frequency will be throttled very early - when reaching a temperature of 75 or 80C. The standard setting in Windows is 97C. Therefore, you might be running only on half the CPU frequency which you could, for many workloads.

Let me show you a couple screenshots:

Running sysbench on 8 threads without the fix

As you can see, it takes my machine 43s to finish the benchmark.

Running the same sysbench benchmark with the fix

Now, the same calculation takes only 18s - less than half the time before! These are reproducible numbers. We realize that the benchmarks would otherwise be rather short. It’s the same result when the benchmarks run substantially longer, too.

If you want to install the workaround yourself, here’s the fix which luckily was already provided by Francesco Palmarini: https://github.com/erpalma/lenovo-throttling-fix