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FusionGuy
join:2001-12-06

FusionGuy

Member

[motherboard] UEFI BIOS

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I put together a system with the ASUS P9X79 Deluxe board and was wondering why do I have the UEFI labels on the drives in the priority list. I have one SSD and optical drive installed.

From the pic this is what is shown. The first is Windows boot manager with the UEFI label > optical drive with Windows 7 DVD and UEFI label > my SSD > optical drive again.

This is the first time I'm using a UEFI BIOS so I'm not familiar with them. So this is what I want to know:

1. Why does the BIOS show a Windows boot manager icon. When I first booted into the BIOS after assembling the PC I only seen the SSD and optical drive.

2. Why do I have two optical drives listed. One is with the UEFI label, the other without. I only have one optical drive. When I remove the DVD from the drive and reboot into the BIOS the one with the UEFI label disappears.

CylonRed
MVM
join:2000-07-06
Bloom County

CylonRed

MVM

Nothing in the manual explains the lists or what would be expected?

FusionGuy
join:2001-12-06

FusionGuy

Member

Nothing to what I'm asking. It just explains the basic stuff.

koitsu
MVM
join:2002-07-16
Mountain View, CA

koitsu to FusionGuy

MVM

to FusionGuy
What did Asus say to your questions?

norwegian
Premium Member
join:2005-02-15
Outback

norwegian to FusionGuy

Premium Member

to FusionGuy
I've not used UEFI but this link would suggest to me it is the UEFI boot manager for protection.

»blogs.msdn.com/b/b8/arch ··· efi.aspx

»en.wikipedia.org/wiki/Un ··· nterface

DarkLogix
Texan and Proud
Premium Member
join:2008-10-23
Baytown, TX

DarkLogix to FusionGuy

Premium Member

to FusionGuy
Just some guesses based on my limited UEFI experience

the ones with the UEFI tag are showing that ti'll try to UEFI boot those before bios booting them.

I would UEFI boot them as thats the only way to have a GPT boot drive, and GPT is said to be more robust than MBR.

koitsu
MVM
join:2002-07-16
Mountain View, CA
Humax BGW320-500

koitsu

MVM

said by DarkLogix:

I would [use] UEFI boot them as thats the only way to have a GPT boot drive ...

Not picking on you or anything mate, but to clarify: that's the only way to have a GPT boot drive on Windows. On FreeBSD we do not have this problem; I happily boot from a GPT partitioned disk on my Supermicro X7SBA motherboard (BIOS only, i.e. non-UEFI). Proof:

root@icarus:/root # gpart show -p ada0
=>       34  156301421    ada0  GPT  (74G)
         34       2014          - free -  (1M)
       2048        128  ada0p1  freebsd-boot  (64k)
       2176    4194304  ada0p2  freebsd-ufs  (2.0G)
    4196480   33554432  ada0p3  freebsd-swap  (16G)
   37750912   33554432  ada0p4  freebsd-ufs  (16G)
   71305344   33554432  ada0p5  freebsd-ufs  (16G)
  104859776   51441679  ada0p6  freebsd-ufs  (24G)
 

Wikipedia provides lots of details. And be sure to see "Legacy MBR (LBA 0)" too, specifically the 2nd-to-last paragraph.

Moral of the story: a properly-written bootloader/bootstrap doesn't require use of UEFI to boot from GPT. Windows is just horribly stupid in this manner.
said by DarkLogix:

... and GPT is said to be more robust than MBR.

"Robust" isn't the right word. I would say GPT addresses some of the shortcomings of the classic MBR scheme, specifically:

* Relies purely on LBA rather than classic CHS (an good riddance!)
* Native support for partitions larger than 2TB
* Supports up to 128 partitions per device (MBR limited to 4) -- but I don't consider this a positive because anyone with that many partitions on a single device should be using a volume manager!

The only thing more "robust" about GPT is that it stores two copies of its header on the disk -- one at LBA 1, and one at the very end of the device.

However, this "robustness" has caused problems for some operating systems -- specifically Linux md (superblock version 1.0 and 1.1 would get their superblocks stomped by GPT (issue fully addressed in 1.2)), and FreeBSD GEOM (still a problem and I doubt it will ever be fixed).