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Comment by jsheard | Hacker News Reader

AMD have acknowledged there is an issue with their mainstream Ryzen CPUs that can cause segfaults on Linux, but they claim it doesn't affect their Threadripper or Epyc models.

http://www.phoronix.com/scan.php?page=news_item&px=Ryzen-Seg...

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It seems to be related to php. A user on reddit which has a Epyc 7551 CPU has no segfaults without the php portion of the test: https://www.reddit.com/r/Amd/comments/6rmq6q/epyc_7551_minin...

People have also reported it when performing parallel compilation using GCC, so it's not limited to PHP.

The segfaults in that particular Reddit thread were caused by a php test suite and are not the high parallel load type of segfault plaguing RyZen.

As of now, nobody seems to be able to reproduce the high parallel load segfaults on epic or threadripper.

AMD says they can reproduce the problem on RyZen, and that it is not present in epic/threadripper.

The PHP issue is a separate cause for segfault that got mistaken for the original linux segfault issue when Phoronix messed that up in that article. Those segfaults also happen with Intel machines. The Ryzen linux segault issue is still not completely clear, but is confirmed by AMD, can be triggered by gcc and is not the same as the PHP issue.

I don't use PHP and have a Ryzen linux machine that hard freezes every so often (around once per week) with nothing in logs. Have pretty much given up on debugging it.

You should contact AMDs support and let them figure it out with you. From what I hear they treat that issue seriously by now, and if your processor turns out to be faulty they should offer you a RMA.

Though hard freezes not during compilation should be a completely different issue, and it will be an effort to pinpoint the processor as responsible.

Yeah, we pretty sure it's not a RAM, PSU, or SATA disk problem (because we had multiples of different kinds to swap around), and we also know that the problem gets much much worse when using an M2 NVMe PCIE SSD (as in hard freezes occur way more frequently, regardless of M2 model). (And it's also possible that the M2 issue is a different problem entirely.) But it could still easily be some kind of motherboard issue. And with it only happening around every 9 days on average... We could contact AMD, but how the heck do we ever narrow down what's going on if we can't trigger replication more frequently? And that's time that my actual job isn't getting done... (I'm personally inclined to think Mobo is at fault.)

Are you monitoring your temps?

The PHP portion segfaults on other CPUs because it's not related to the real problem.

In the LinusTechTips review he mentioned only top 5% dies go into Threadripper. So if it's related to quality of Ryzen, then that might make sense. I'd be surprised if Threadripper isn't plagued by this bug, though.

Except the Threadripper dies are closely related to the Epyc dies (ECC, PCIe lanes. etc), not the Ryzen cores.

No, you've got that wrong.

TR uses the same Zeppelin dies as Ryzen. Just the top 5% binned parts.

Epyc uses a newer die stepping that isn't yet used for Ryzen or TR.

Thanks for the clarification!

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