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Category: Technical Support
Forum Name: AMD Motherboards
Forum Description: Question about ASRock AMD motherboards
Printed Date: 14 Nov 2018 at 10:18am
Software Version: Web Wiz Forums 11.06 -

Posted By: parsec
Date Posted: 17 Nov 2017 at 12:12pm
If you are installing Windows 10 on an ASRock X399 board, please read this information to potentially save yourself from your new installation failing to boot for no apparent reason.

If your version of Windows 10 is 1607 (RS1) or earlier, please set the IOMMU option to Disabled in the UEFI/BIOS before you try to install Windows 10. The IOMMU option is in the Advanced\North Bridge Configuration screen. The default value of Auto for this option is Enabled. Don't forget if you do a UEFI/BIOS clear, the IOMMU feature will be reset to Auto/enabled. You'll need to reset it to Disabled if you want to use a Windows 10 RS1 version.

If the IOMMU option is enabled in the UEFI, after installing Windows 10 RS1, the PC will begin loading Windows, but freeze at that point. That is caused by the Windows 10 RS1 versions not supporting the IOMMU feature.

Windows 10 RS2 versions support the X399/ThreadRipper IOMMU feature, so won't have this issue after the installation.

If you have an older Windows 10 disk or ISO download USB installer, please go to the Microsoft page below, and use their Media Creation tool to download the latest version of Windows 10. When you run this tool, please be sure to select the Create installation media (USB flash drive, DVD, or ISO file) for another PC option. You can then select the creation of a USB flash drive installation media, or saving the download as an ISO file. You may use the license key from an older Windows 10 optical disk, etc, to activate the new version of Windows 10 downloaded with the media creation tool." rel="nofollow -

The issue with early versions of Windows 10 not supporting the X399/ThreadRipper IOMMU feature is also true for Windows 7, 8, and 8.1. While those versions of Windows are not officially supported by the X399/ThreadRipper platform (for other reasons), if you choose to use any of those versions of Windows, you also should (must) disable the IOMMU feature in the UEFI/BIOS.

Users of other OS types, such a Linux, should disable the IOMMU feature if you are unsure that the OS or version of that OS supports the X399/ThreadRipper IOMMU feature.

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Posted By: HappyChubb
Date Posted: 17 Jan 2018 at 2:32pm
My experience precisely.

Appreciate your thorough assessment of this issue. Additionally, I had to disable the CMS setting (bottom selection under "Boot" tab) in order to get Windows to boot & load properly.

All BIOS settings returned to their defaults after flashing the BIOS, so I had to manually disable these settings again.

Great advice, parsec.

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