Comments on: Using UEFI DUET to boot Fedora 12 http://blog.fpmurphy.com/2009/12/using-uefi-duet-to-boot-fedora-12.html of an OS plumber Thu, 09 Feb 2012 11:45:22 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Morgan Herley http://blog.fpmurphy.com/2009/12/using-uefi-duet-to-boot-fedora-12.html/comment-page-1#comment-94 Morgan Herley Mon, 22 Nov 2010 10:56:29 +0000 http://blog.fpmurphy.com/?p=306#comment-94 Decent reading. Like your site design as well. Keep up your good work. Decent reading. Like your site design as well. Keep up your good work.

]]> By: fpmurphy http://blog.fpmurphy.com/2009/12/using-uefi-duet-to-boot-fedora-12.html/comment-page-1#comment-51 fpmurphy Mon, 26 Jul 2010 20:01:15 +0000 http://blog.fpmurphy.com/?p=306#comment-51 > The limit of the 2tb booting is not the BIOS, it's the MBR table. Correct. I have removed the sentence that implied a BIOS limit. Thank you for spotting the error. > There is no reason a normal BIOS machine with a GPT installed couldn't boot from a partition > 2TB. I agree. > Since GPT requires the legacy MBR still be present Huh? Where did that requirement come from? You can have a GPT without having an MBR present. In fact you can embed a BIOS boot partition inside GPT if you want to. The T13 (ATA) GPT partition record design now includes a Legacy BIOS Bootable bit that can be set for a partition like a BIOS boot partition. The algorithm is documented in T13 EDD-4 revision 2 and later. But again there is no requirement for an MBR to be present. > Not only is booting from GPT without EFI possible, it's actually fairly easy. Correct. Just look at GRUB2. > The limit of the 2tb booting is not the BIOS, it’s the MBR table.

Correct. I have removed the sentence that implied a BIOS limit. Thank you for spotting the error.

> There is no reason a normal BIOS machine with a GPT installed couldn’t boot from a partition > 2TB.

I agree.

> Since GPT requires the legacy MBR still be present

Huh? Where did that requirement come from? You can have a GPT without having an MBR present. In fact you can embed a BIOS boot partition inside GPT if you want to. The T13 (ATA) GPT partition record design now includes a Legacy BIOS Bootable bit that can be set for a partition like a BIOS boot partition. The algorithm is documented in T13 EDD-4 revision 2 and later. But again there is no requirement for an MBR to be present.

> Not only is booting from GPT without EFI possible, it’s actually fairly easy.

Correct. Just look at GRUB2.

]]> By: Billy http://blog.fpmurphy.com/2009/12/using-uefi-duet-to-boot-fedora-12.html/comment-page-1#comment-50 Billy Mon, 26 Jul 2010 19:46:27 +0000 http://blog.fpmurphy.com/?p=306#comment-50 First, I would like to say, pretty good overall, but a good amount of miss information as well. The limit of the 2tb booting is not the BIOS, it's the MBR table. There is no reason a normal BIOS machine with a GPT installed couldn't boot from a partition > 2TB. Since GPT requires the legacy MBR still be present, there is no reason the code stored in the MBR couldn't boot from any location, in any partition (no matter the size) stored in the GPT. It's just companies want you to believe that it's impossible and you must upgrade. I have written my fair share of software (including my own MBR, multiple boot loaders, and small operating systems) and can confirm that you can access > 2tb using bios functions, so the only limitation is purely implementation of the software. Not only is booting from GPT without EFI possible, it's actually fairly easy. First, I would like to say, pretty good overall, but a good amount of miss information as well. The limit of the 2tb booting is not the BIOS, it’s the MBR table. There is no reason a normal BIOS machine with a GPT installed couldn’t boot from a partition > 2TB. Since GPT requires the legacy MBR still be present, there is no reason the code stored in the MBR couldn’t boot from any location, in any partition (no matter the size) stored in the GPT. It’s just companies want you to believe that it’s impossible and you must upgrade. I have written my fair share of software (including my own MBR, multiple boot loaders, and small operating systems) and can confirm that you can access > 2tb using bios functions, so the only limitation is purely implementation of the software. Not only is booting from GPT without EFI possible, it’s actually fairly easy.

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