AMD Motherboards - X399M + RESIZEABLE BAR

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X399M + RESIZEABLE BAR

Printed From: ASRock.com
Category: Technical Support
Forum Name: AMD Motherboards
Forum Description: Question about ASRock AMD motherboards
URL: https://forum.asrock.com/forum_posts.asp?TID=19172
Printed Date: 08 Aug 2025 at 12:15pm
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com

Topic: X399M + RESIZEABLE BAR

Posted By: MrWavel
Subject: X399M + RESIZEABLE BAR
Date Posted: 28 Jun 2021 at 9:03pm

Hello there,

I upgraded to version P3.81[BETA] to test the resizable bar thing with my VEGA64.

When i enable BAR option and disable CSM (mandatory) my nvme won't boot and I'm unable to use windows.

Has anyone ever experienced this ?

(if I deactivate the BAR option, everything returns to perfect normal)

Replies:

Posted By: crion
Date Posted: 29 Jun 2021 at 4:47pm

Well yes, when you disable CSM your boot disk needs to be set for UEFI boot (GPT layout).

https://docs.microsoft.com/en-us/windows/deployment/mbr-to-gpt" rel="nofollow - https://docs.microsoft.com/en-us/windows/deployment/mbr-to-gpt

This can be trivial but I needed a couple of tweaks to get the disk layout to change to GPT.

'sminfo' can verify if BIOS is in Legacy or UEFI.

run chkdsk before on disk so that you know it's in good condition.

Posted By: crion
Date Posted: 29 Jun 2021 at 4:50pm

It works perfectly with 3.81 X399 Fatal1ty and ASUS ROG STRIX 3090 flashed to latest FW.

I think the system feels better to handle several GPU loads at the same time, with less stuttering/slowdowns.