Ryzen C-State related problems -- what is the root cause?

I would like to know why is that we are advised to disable C-State feature in the BIOS, to improve stability and such. For instance I do find Unraid, working good after disabling C-state.
So what is going on ???
Is the issue with Ryzen silicon OR
is it with the loadable microcode OR
Is it with kernel of the operating systems, not yet adapted to utilized the C-states feature properly ??
why would BIOSs ship with them enabled by default, if they know things may not work properly for many ???!!!:roll_eyes:

ACPI implementation is horrible because vendors use the spec as a suggestion rather than a guideline.
Power delivery issues possibly.
a.3 possibly due to the newness of the platform and the fact that AMD has spread themselves so thin with all of their initiatives that Intel optimizations seem to perform better than AMD optimizations (gcc, llvm, arch, etc).

1 Like

Let me hope that it can be fixed in software …
Wish we had some kind of processor test/diagnostic board like the one below, to test them all!
Has anybody found AMD Ryzen’s errata document ??

I wish. Currently the BKDG (Bios and Kernel Developers Guide) is still only available under NDA.
The public stuff is comprised of the 17h documents on here:

Which Includes the Registers reference, the Processor Programming Reference and Software optimization guide. Some prior documents still apply such as for the PSP.

Some reverse engineered stuff on the Ryzen Pipeline here:


And whatever I’ve previously dumped here:

And probably a good deal more stuff I’m forgetting about.

But no errata spec/BKDG.

Most of the errata (atleast the fixed ones) are currently best found by looking at the linux kernel.


Errata for Ryzen/Threadripper/EPYC has finally come now… :grinning:

There are a lot of “Suggested Workarounds” presented!
Note sure if System Software meant the Linux kernel or AGESA or either of them, depending upon the issue.



@noenken - This means you may soon get some stability improvements for your Raven Ridge Laptop.

It is actually running perfectly fine for a few weeks already. :wink:
And yes, C-States again. Motherfucking C-States.


How much watts would be the power delta that we are talking about ?