OSDev.org

The Place to Start for Operating System Developers
It is currently Thu Mar 28, 2024 10:36 am

All times are UTC - 6 hours




Post new topic Reply to topic  [ 7 posts ] 
Author Message
 Post subject: OS not booting on legacy mode UEFI machines
PostPosted: Fri Jun 16, 2017 2:27 pm 
Offline

Joined: Wed Feb 08, 2017 7:51 pm
Posts: 22
Hi.

So I have a MBR bootloader that is defined as such:

Code:
(510 bytes of code)
dw 55AAH
(more code)


This works for machines that do not have UEFI support entirely.
But machines that support UEFI (I have two of them, one is older than the other), they can't boot off of my imaged usb drive.
I am confused as to why this is happening. Should I have a FAT header before my code?
Does anyone know why this is happening?

thanks


Top
 Profile  
 
 Post subject: Re: OS not booting on legacy mode UEFI machines
PostPosted: Fri Jun 16, 2017 2:56 pm 
Offline
Member
Member
User avatar

Joined: Fri Feb 17, 2017 4:01 pm
Posts: 640
Location: Ukraine, Bachmut
Quote:
5.2.1 Legacy Master Boot Record (MBR)
A legacy MBR may be located at LBA 0 (i.e., the first logical block) of the disk if it is not using the
GPT disk layout (i.e., if it is using the MBR disk layout). The boot code on the MBR is not executed
by UEFI firmware.


But in your case, that even is not a valid MBR.

_________________
ANT - NT-like OS for x64 and arm64.
efify - UEFI for a couple of boards (mips and arm). suspended due to lost of all the target park boards (russians destroyed our town).


Top
 Profile  
 
 Post subject: Re: OS not booting on legacy mode UEFI machines
PostPosted: Fri Jun 16, 2017 6:36 pm 
Offline
Member
Member
User avatar

Joined: Sat Jan 15, 2005 12:00 am
Posts: 8561
Location: At his keyboard!
Hi,

interruption wrote:
So I have a MBR bootloader that is defined as such:

Code:
(510 bytes of code)
dw 55AAH
(more code)


There's multiple problems with booting from USB flash, so I thought I'd start a "Problems Booting From USB Flash" page in the wiki. :)


Cheers,

Brendan

_________________
For all things; perfection is, and will always remain, impossible to achieve in practice. However; by striving for perfection we create things that are as perfect as practically possible. Let the pursuit of perfection be our guide.


Top
 Profile  
 
 Post subject: Re: OS not booting on legacy mode UEFI machines
PostPosted: Sat Jun 17, 2017 10:10 am 
Offline
Member
Member

Joined: Mon Mar 25, 2013 7:01 pm
Posts: 5099
Brendan wrote:
There's multiple problems with booting from USB flash, so I thought I'd start a "Problems Booting From USB Flash" page in the wiki. :)

Looks good! One thing bothers me though.

Quote:
Some firmware vendors have decided that USB flash devices should also be able to emulate CD, and support the El Torito specification for USB flash devices.

Do you have any proof for this statement?


Top
 Profile  
 
 Post subject: Re: OS not booting on legacy mode UEFI machines
PostPosted: Sat Jun 17, 2017 4:49 pm 
Offline
Member
Member
User avatar

Joined: Sat Jan 15, 2005 12:00 am
Posts: 8561
Location: At his keyboard!
Hi,

Octocontrabass wrote:
Quote:
Some firmware vendors have decided that USB flash devices should also be able to emulate CD, and support the El Torito specification for USB flash devices.

Do you have any proof for this statement?


I don't have proof and can't remember where I saw it mentioned. I may have got this around the wrong way (some USB flash devices emulate USB CD devices).


Cheers,

Brendan

_________________
For all things; perfection is, and will always remain, impossible to achieve in practice. However; by striving for perfection we create things that are as perfect as practically possible. Let the pursuit of perfection be our guide.


Top
 Profile  
 
 Post subject: Re: OS not booting on legacy mode UEFI machines
PostPosted: Sun Jun 18, 2017 9:36 am 
Offline
Member
Member

Joined: Mon Mar 25, 2013 7:01 pm
Posts: 5099
I've only ever heard of hybrid ISOs being bootable when written to a USB flash drive. I think the statement on El Torito in the article should be removed until someone can make a more compelling argument.


Top
 Profile  
 
 Post subject: Re: OS not booting on legacy mode UEFI machines
PostPosted: Mon Jun 19, 2017 10:40 pm 
Offline
Member
Member

Joined: Fri Aug 26, 2016 1:41 pm
Posts: 671
interruption wrote:
Code:
(510 bytes of code)
dw 55AAH
(more code)

This is only an addendum to the other answers regarding booting USB media. But the first thing that struck me is that your boot signature is incorrect. Expressed as a word the boot signature is actually dw 0AA55h or two individual bytes db 55h, 0AAh


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 6 hours


Who is online

Users browsing this forum: DotBot [Bot], Google [Bot], Majestic-12 [Bot] and 61 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group