Mobile Ryzen BIOS, IOMMU, Power...

Discussion created by voyageur on Mar 6, 2019
Latest reply on Mar 11, 2019 by voyageur

I own a laptop with a Ryzen 2500u CPU and like other users of mobile Ryzen CPUs, have had to manually edit boot parameters to get Linux to work. FreeBSD, NetBSD... don't boot either, even though they are modern enough to run on standard x86-64. We have a long forum thread at Lenovo about this and there are numerous reports online regarding the "ivrs table" which is at the root of this issue.


Our Lenovo thread.

A reddit thread with various shared experiences.

An acer thread mentioning this.

Someone with a Dell on askubuntu.


I was surprised to see posts here from users of Acer and HP laptops built on Ryzen without any mention of this issue so I decided to start a thread in the hopes that AMD will investigate and provide a universal solution to the vendors so they can provide a bios update. While Windows 10 is able to boot, the "AMD IOMMU Device" is absent. This device is present on other AMD systems.


I expect and have read the typical responses about only Windows being supported or that it's up to the vendor to update the bios. I strongly feel that AMD should first ensure that mobile Ryzen cpus provide a standard x86-64 system interface. This would allow our systems to run well-known and venerated Operating Systems that are currently unable to boot. (UNIX, Windows 7...) Many people, like me, try out or have to work with OS's besides Windows 10 and this issue adds a significant obstacle to the usual tinkering required to get them working.


Ryzen laptops perform admirably so I am encouraged that AMD is finally including the Raven Ridge cpus in the standard driver packages. To that end, I would also like to report an issue with Windows CPU power management that I believe can be easily fixed at the source.


In Windows Power Plan > Change advanced power settings > Processor power management,  we should be able to set a "Maximum processor state" to limit the maximum cpu frequency. It is meant as a battery-saving feature and, in fact, Windows sets 70% here when "Battery saver" plan is selected. This does not work as it should. Setting anything besides 100% limits the cpu to 1600MHz. Correct operation would allow the cpu to boost normally but only up to the set maximum.


Thank you for continuing to advance technology and for taking the time to read this. I hope someone will look into this.