Legacy & UEFI booting on USB

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arcon

423 posts

Ultimate Geek

#214251 3-May-2017 20:19

I have Win7 64 bit and an Asus Z-97A USB 3.1 mobo, latest BIOS.

I'm trying to boot onto a USB stick in Legacy mode, but the only boot options for USB in the BIOS are UEFI. Its a UEFI BIOS but it supports both modes (supposedly). Booting in UEFI does not help me if I want to restore disk backups made with Acronis True Image 2017; my OS was installed Legacy & I'm told by Acronis that the rescue media needs to be booted in the same environment for disk restores to work.

This is speculation but could the BIOS's Secure Boot feature be preventing Legacy USB bootup on USB? If so, there's no way to disable Secure Boot (thanks Asus), other than maybe deleting all the Bios security keys... is that safe? lol.

Any other advice is welcome.

solutionz

589 posts

Ultimate Geek
Inactive user

#1775157 3-May-2017 21:25

Shouldn't have any problem deleting the keys, they can be re-added.

See: https://www.all4os.com/windows/disable-asus-motherboards-uefi-secure-boot.html

1024kb

1168 posts

Uber Geek

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Lifetime subscriber

#1781973 14-May-2017 16:14

The whole UEFI/Legacy/CSM boot option thing is a mess in most UEFI control panels. The layout is far from intuitive, that's for sure. But hey, this is IT, baffle them with bulls*** then charge like a wounded bull - seems to have worked for Gates, Ellison et al.

You won't get Legacy offered with Secure Boot enabled, & you often (usually) won't have all the options on the same page - you'll have to flip back & forth between Boot & Security pages.

Security is where you can switch Secure boot off - do this first (don't need to delete keys, just switch it off) then flip back to the Boot page, turn Legacy/CSM on. You may need to reboot once & return to UEFI control panel to set your boot drive options.

If you use Rufus to create your bootable USB drive, check the target system type that boots BIOS or UEFI rather than one or the other.

Megabyte - so geek it megahertz

richms

28192 posts

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#1781976 14-May-2017 16:23

Worse is that you cant repair a windows 7 install unless it was booted the same way as the installed version. I have fixed many friends systems where they couldnt repair just by waiting for the second press something to boot message from the windows DVD when booting.

I had to follow a massive long involved process to make a UEFI bootable usb drive for windows 7 as well.

Made worse by stupid lack of error messages from apps about whats going on, inability to see how things were booted.

Richard rich.ms

arcon

423 posts

Ultimate Geek

#1783806 17-May-2017 17:48

It turns out that in addition to the Secure Boot issue, my mobo only allows USB3.x sticks for storage, not booting. USB2.0 sticks must be used. Lol, would've been nice for Asus to specifically mention that, but whatevs.

I've now done my first successful backup & restore yay.

1024kb

1168 posts

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#1783809 17-May-2017 17:58

Still love your Microsofts? Or really, really wish for a viable alternative?

Megabyte - so geek it megahertz

arcon

423 posts

Ultimate Geek

#1783816 17-May-2017 18:29

1024kb: Still love your Microsofts? Or really, really wish for a viable alternative?

Um... bios support has nothing to do with the operating system

vulcannz

436 posts

Ultimate Geek
Inactive user

#1784589 19-May-2017 09:00

Sometimes the USB partition block size makes a difference as well (ie some BIOS don't seem to like 4096).

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jhsol

102 posts

Master Geek

#1784598 19-May-2017 09:29

1) The Motherboard BIOS settings determine whether Legacy or UEFI is used at boot. They will support either Legacy only, Hybrid (both Legacy and UEFI), or UEFI only.

On the z97a this is set in the CSM setting (i believe).

If you watch the youtube vid https://www.youtube.com/watch?v=kJs1nY8_CY0 @ the 7.07 mark it shows the area where you should be looking. CSM should be where you put it into hybrid mode.

2) Secure boot is only available in UEFI mode as its a feature of that platform. Secure boot is not an OS limited thing as this is available for both Linux and Windows versions that support it.

3) Some Motherboards will not boot off a USB3 port. This is usually limited to older motherboards and is due to the OS boot loader not containing the USB3 drivers required for the motherboard being used. You usually can have success by plugging the USB3 Stick into a USB2.0 port. Alternatively a USB2.0 stick will sometimes work in a USB3 port simply because the port is running at 2.0 specs.

What Motherboard (or PC) do you have?