[SOLVED] Resizeable Bar: Configurations necessary.

[DaveB_55]

Hello, I have a MSi z390 MPG Gaming Pro AC motherboard which is Resize Bar compatible and a EVGA RTX 3090 XC3 Ultra and was just had some questions about the configurations that are needed to use Resizeable Bar.

As far as I know, 11th and 12th gen intel cpus are supported, but with the most recent update to my motherboard I was interested in seeing if my 9700k cpu would work with Resizeable Bar.

One problem with Resizeable Bar compatibility with 9th gen motherboards that I've read is that users are required to disable CSM (or Legacy) Boot in BIOs or they will face a black screen when enabling Resizeable Bar. For my setup I made sure that I my Windows HD was formated and running in UEFI mode, not Legacy. While my Windows is indeed formatted in UEFI I've realized that my second hdd is formated in Legacy mode, this my current Boot setting in bios is actually Legacy/UEFI Boot.

My question is, do I have to set my BIOS to UEFI Boot only? And if so, would that make my secondary storage hdd that's donated in Legacy mode not detectable when booting I'm UEFI only mode?

 

[InvalidError]

The only difference with UEFI boot is that you won't be able to access devices that only have legacy BIOS extensions (ex.: pre-UEFI add-on SATA and USB cards) at boot.

The OS should still be able to detect and load drivers as needed. That's how people can get legacy GPUs to work on UEFI-only systems by using the IGP or secondary GPU for boot, likewise the other way around with UEFI-only GPUs on legacy-only motherboards, both work equally fine once you get in the OS using the IGP and install the appropriate dGPU drivers.

 

[DaveB_55]

As you can see, my C: Drive (Windows) is formated in UEFI format but my second HDD used for additional storage is formated in legacy (MDR). Honestly, I'm not really sure what any of this means but I just want to be sure that there won't be any incompatibility with drive E: if I change my boot option from "Legacy/UEFI" to just "UEFI".

And again, I'm not really sure why people have an issue with enabling Resizeable Bar with CSM/Legacy, but disabling CSM and booting into UEFI only mode was recommended when enabling Resizeable Bar to avoid getting a black screen on boot.

 

[InvalidError]

There is no such thing as "UEFI format" or "Legacy" format. UEFI/Legacy only affects how the BIOS will present devices to the OS' bootloader with only UEFI devices being present in a UEFI-only boot config. This has absolutely nothing to do with how the HDD/SSD partitions have been setup (GUID vs MBR) by whatever OS got installed first.

 

[DaveB_55]

The only difference with UEFI boot is that you won't be able to access devices that only have legacy BIOS extensions (ex.: pre-UEFI add-on SATA and USB cards) at boot.

I think I understand, but how would I be able to tell if my HDD's are UEFI compatible? I apologize for my incompetency lol.

 

[InvalidError]

I think I understand, but how would I be able to tell if my HDD's are UEFI compatible? I apologize for my incompetency lol.

It makes absolutely no difference as far as HDDs are concerned. UEFI vs Legacy only affects how the BIOS presents the SATA controller or NVMe SSDs to the OS' bootloader. It does not care about what is on the HDDs or SSDs, that is for the OS' bootloader to figure out. All UEFI or Legacy does is tell the bootloader where to start from.

 

[DaveB_55]

It makes absolutely no difference as far as HDDs are concerned. UEFI vs Legacy only affects how the BIOS presents the SATA controller or NVMe SSDs to the OS' bootloader. It does not care about what is on the HDDs or SSDs, that is for the OS' bootloader to figure out. All UEFI or Legacy does is tell the bootloader where to start from.

So I changed the boot mode from UEFI/Legacy to UEFI in BIOS and my secondary HDD disappeared from the boot order. Does that mean that my HDD won't boot in UEFI mode?

 

[InvalidError]

So I changed the boot mode from UEFI/Legacy to UEFI in BIOS and my secondary HDD disappeared from the boot order. Does that mean that my HDD won't boot in UEFI mode?

As long as your actual boot drive - the one with the OS on it - shows up, you shouldn't need anything else.

The UEFI boot isn't showing your other HDD as a boot device because UEFI cannot boot on MBR, it needs the legacy layer for that. The OS will still be able to use the drive fine once the necessary drivers are loaded.