[SOLVED] How do I get my computer to install Win 10 in UEFI Mode?

[1405]

I have tried everything I can think of. I have a SSD that I even used diskpart on to clean and convert gpt to GPT format. Select disk in diskpart shows it is a gpt disk. But Win 10 install keeps installing itself in legacy mode. My motherboard is set to default BIOS values where CSM mode is enabled.
BIOS is latest version. I'll be happy to provide more info as needed.

Gigabyte B450M DS3H
Ryzen 5 2600
Team SATA 3.5" SSD

 

[NightHawkRMX]

Maybe an option for legacy+UEFI or UEFI only. UEFI only is wanted.

Also, are you using 32bit or 64 bit w10

 

[kerberos_20]

CSM mode should be disabled or atleast storage boot option should be set to uefi

 

[1405]

OK. When I reset the BIOS to default, it has CSM support as enabled and both storage boot option and other PCI Device ROM Priority as legacy. If I understand you guys right, I should disable CSM Support.

OK. Did the above and now the other two storage options are gone. I will try to install Win 10 again tomorrow because I will be getting a new M.2 PCIe x4 SSD to replace my 3.5" SATA. Thank you.

Btw, this BIOS doesn't seem to have a "UEFI + Legacy" option, just UEFI or Legacy.

 

[lynx1021]

I had to turn off "secure boot" to boot to a cloning program to clone my hard disk to a SSD on my windows 8.1 UEFI laptop.

 

[NightHawkRMX]

Disabling secure boot has helped me with simmilar issues in the past. Put it into uefi mode if possible.

 

[Colif]

Some gigabyte motherboards have a Win 8/10 OS menu that auto selects and disables certain features. including turning on secure boot and turning off csm.

Windows 8/10 Features
Allows you to select the operating system to be installed.

• Other OS (Default)
• Windows 8/10
• Windows 8/10 WHQL

CSM Support
Enables or disables UEFI CSM (Compatibility Support Module) to support a legacy PC boot process.

• Enabled - Enables UEFI CSM. (Default)
• Disabled - Disables UEFI CSM and supports UEFI BIOS boot process only.

This item is configurable only when Windows 8/10 Features is set to Windows 8/10 or Windows 8/10 WHQL

source

It seems odd a Newish motherboard would default to CSM. And not default to UEFI instead.

Boot Option Priorities
Specifies the overall boot order from the available devices. Removable storage devices that support GPT format will be prefixed with "UEFI:" string on the boot device list. To boot from an operating system that supports GPT partitioning, select the device prefixed with "UEFI:" string.
Or if you want to install an operating system that supports GPT partitioning such as Windows 10 64-bit, select the optical drive that contains the Windows 10 64-bit installation disk and is prefixed with "UEFI:" string.

CSM Support Enables or disables UEFI CSM (Compatibility Support Module) to support a legacy PC boot process.
Enabled Enables UEFI CSM. (Default).
Disabled Disables UEFI CSM and supports UEFI BIOS boot process only.

its likely that the choice that enables it isn't at expense of UEFI, but rather supports both. As disabled shows it only supports the one. This is more likely as I helped someone with a slow boot on a B360 and turning CSM off sped it up as PC had less choices

I would disable CSM, boot from the USB marked UEFI and it will install as GPT as it wants to and sees hardware supports it.

 

[kerberos_20]

It seems odd a Newish motherboard would default to CSM. And not default to UEFI instead.

mine board defaulted to CSM aswell, but it has legacy+uefi options set as default
not sure about his, could be that it detects it based on connected devices (harddrives with mbr, legacy add in cards with bios opt rom)

 

[Colif]

in hindsight, having CSM as default makes sense as not all people buying the boards intend to install windows and I think there are still some OS out there that still use legacy.

With csm mode on, it means at startup, the PC will either try CSM or UEFI boot method to find the installer. Mine has similar and one time installing win 10 I ran into the "this hard drive is wrong format to install windows on error" as I had done what i always had before (in win 7), deleted the C partition and clicked next... I wasn't sure what to do with that message and turned PC off confused that a drive that had just had win 10 on it 5 minutes before wouldn't install it now.

A few minutes later I started PC and deleted all the partitions and clicked next and during the restart, the bios had swapped to legacy boot method and installed win 10 as Legacy. This was all long before I started answering questions here, I know a lot more now.

Having CSM off forces it to use UEFI/GPT as it is the only boot method that works.

 

[1405]

OK. I think I understand this CSM thing now. I did as instructed and disabled CSM. Win10 installed in URFI mode all by itself from a new SSD. Thank you all for your help.