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I just built new PC based on Asus Z87-Plus motherboard and in BIOS boot menu I now have my removable devices listed twice - once as a device itself and once with "UEFI: " prefix.

It looks like this for Blu-ray drive on SATA port 5:

P5: PIONEER BD-RW BDR-208M (3523 MB)
UEFI: PIONEER BD-RW BDR-208M (3523 MB)

USB flash drives are similarly listed twice.

Hard drives are only listed once as non-UEFI.

What are the implications of picking UEFI boot option vs non-UEFI? Why aren't hard drives available in boot menu with UEFI option?

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2 Answers

up vote 3 down vote accepted

The non-UEFI option will boot the device in the legacy BIOS mode. If you have a Win7/8 DVD it can be booted in either BIOS or UEFI mode. If you have a GPT partitioned boot drive then you need to install Windows in UEFI mode.

Once you install an OS in BIOS or UEFI mode, to switch modes you'll need to reinstall the OS (with Windows at least), so guess for hard drives only the mode the OS is installed in is shown.

Dynamically selecting modes is thus generally useful only for USB or DVD drives.

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Displaying only a single mode for the HDD might also be a quirk of your motherboard. See this page for a motherboard that allows the user to boot the same Hitachi HDD in either BIOS or UEFI mode. –  Karan Jul 6 '13 at 18:20
    
But what is the difference between Windows installed in UEFI mode vs Windows installed in BIOS mode? –  Joe Schmoe Jul 6 '13 at 22:05
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UEFI mode is supposed to have advantages such as helping boot up faster, support for Secure Boot (with Win8) and so on. Also, it's required for booting off GPT drives larger than 2TB (GPT also doesn't have the 4 primary partition limit that MBR does). Other than that Windows itself won't exhibit any difference in behaviour AFAIK. –  Karan Jul 6 '13 at 22:48
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Please claify your question:

Why aren't hard drives available in boot menu with UEFI option?

UEFI is a very complex topic to explain, even for superusers. Do have a read on the WikiPedia entry.

PS. This was supposed to be a comment, but I am still not allowed to make comments.

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