The Workaround To Boot Linux On AMD Threadripper 3960X/3970X Systems

As outlined in our AMD Ryzen Threadripper 3960X / 3970X Linux review, these new Zen 2 Threadripper processors are phenomenal processors that offer significant uplift over earlier Threadripper CPUs and easily dominate over Intel's Core i9 HEDT competition. But there is one big issue right now with the Linux support: on Ubuntu and the like, it doesn't boot without a workaround. Here's that workaround for easy future reference.

See the details in our 3960X/3970X Linux article for more information, this is just a quick public service announcement for those that may have problems booting Threadripper 3900X series processors with TRX40 motherboards and wondering what's going on and looking for a solution...

With the two motherboards AMD supplied as part of the reviewer's kit and the AMD Threadripper 3960X/3970X, all the combinations yielded a system that appears to hang on boot like shown above. But as you can see, if just looking at the tail of the kernel output there isn't any hints. This doesn't seem to be an isolated issue either as other reviewers had asked me if/how to get the new Threadripper processors running on Linux. This is unrelated to the earlier RdRand trouble or other Ryzen/Zen issues with previous launches.

Fortunately, after figuring out it was an MCE issue and knowing about mce=off as a kernel module parameter. That worked for working around the issue.

So if you have boot hangs or issues booting a new Threadripper system, set mce=off as part of your kernel command line parameters. That should workaround the issue.

As pointed out in the formal article, after asking AMD's Linux engineers about the problem, they do have an MCE patch pending. However, as of writing that patch hasn't yet made it into the mainline kernel -- it's not in Linux 5.4 final or the early MCE/RAS changes for Linux 5.5. Hopefully it will make it in as a fix soon to the mainline kernel and get back-ported to stable.

So for now be aware of this one shortcoming in the Linux support but that it can be easily worked around by disabling the machine check exception kernel code. Now if you didn't already, go check out the impressive Threadripper 3960X/3970X Linux benchmarks. More tests are on the way too.