Dual boot EFI and Legacy BIOS

Discussion in 'Windows 7' started by eidassan, Jan 23, 2013.

  1. eidassan

    eidassan MDL Novice

    Jan 22, 2013
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    OK, the threads here typically discuss dual booting from separate partitions or discs. But nearly all do so in the context of a single platform, be it EFI or the classic BIOS. For various reasons I'd like to know the risks and chances for success of doing this across both systems.

    Meaning: I've an OEM Win 7 Home pre-installed on an EFI/gpt disc. On the other internal mbr disc I'd like to place Win 7 Pro using the Legacy BIOS. Yes, I know I could convert the mbr to gpt and let EFI run the whole show, but then this would not be a 'true' and independent dual boot would it? So, will this work? Will there be conflicts? Will the gpt disc see the mrbr disc and vice versa? Will the respective OSs NOT overwrite the other's boot files/partitions and remap memory? In a word, will a state of democracy prevail on my computer?

    I'm willing to forego the EasyBCD route in regards to the dual boot screen and simply use Boot override esc key on my Asus when I want to boot into the MBR disc. Thanks for your help.
     
  2. Flipp3r

    Flipp3r MDL Expert

    Feb 11, 2009
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    I don't think you can dual boot uefi & legacy. Many boards have a bios/uefi switch to select legacy or uefi mode.
    For instance all the new MSI notebooks default to uefi (optimised) so even trying to boot my usb key I can only boot in uefi mode...
    Having just said that, my msi motherboard does let me boot my usb key in any mode?!

    Now I'm thinking... Nah, it's one or the other...
     
  3. eidassan

    eidassan MDL Novice

    Jan 22, 2013
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    Flipp, that's pretty much the consensus I've gotten everywhere: nobody really knows. No one's tested it. My Aptio designed BIOS/motherboard also gives me the choice on a one-time boot as to whether I want run my USB drive on through the default UEFI Win 7 boot loader or Legacy. But that misses the whole point. It assumes that the dual installation has already worked. It doesn't answer the base question as to whether even if the motherboard has allowed you to fork over, once, into your second disk under, say, Legacy/mbr, once you're there will that disk read anything on the other gpt disk and/or will it already have erased the boot partition on that first EFI disk. I mean it's one of those either very obvious or very obscure questions. But, unfortunately I've yet to find a single post over three well-respected tech sites such as yours that has been able to give a cut and dry answer about it. EFI + EFI or BIOS + BIOS = little or no problem. Yet Flipp, with all respect, your answer typifies the confusion about this issue in a nutshell: EFI + BIOS = er, well, I'm not sure. I could become my own guinea pig, of of course, with all the risks, but it seems hard to imagine with all those guru hackers out there that this problem hasn't already been debugged long ago.
     
  4. Flipp3r

    Flipp3r MDL Expert

    Feb 11, 2009
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    Implementation of UEFI is relatively new to mainstream pc's. As a result there's a lot of confusion. It's only recent that video cards started getting the gop features too.
    I think most of these uefi/bios' are hybrid. MBR (Master boot record) is read from the hdd but "windows boot manager" is in the nvram (I pretty sureo_O).

    Sorry I can't be of more help but I think your stuck on this one...
     
  5. tnx

    tnx MDL Expert

    Sep 2, 2008
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    In the BIOS there will be a setting for either UEFi or Leggacy or BOTH..

    My thinking is, if it is set to both will it let you.

    If you have one drive set to GPT and have windows loaded onto it you set it to first boot the BIOS will recognise what sort it is and away you go.

    Then if you have another drive set to MBR with a different windows loaded onto it and you then select to first boot from that it should let you..

    i have my main OS and main storage drive both set to GPT and my OS drive is UEFI but I also have a couple of other HDD'S which get plugged in and out via hotswap which are not GPT and these work fine...

    Later I will have to test loading XP Pro SP3 onto a MBR HDD and see if dual booting does work
     
  6. eidassan

    eidassan MDL Novice

    Jan 22, 2013
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    Flipp and tnx, thanks to you both, I finally found people who are at least tuned into the problem. It partly boils down to what uefi/legacy hybrid bios means and how to recognize it in your bios. A post on another site has given me some intuition into the matter. My Asus N76vm has the American Megatrends v211 which doesn't have an option to 'Launch UEFI'. It does have a configuration mode 'Launch PXE OpRom' with an info window that explains 'Controls the execution of UEFI and Legacy PXE OpRom'. Does PXE OpRom = Legacy BIOS, or is this something else. Oddly, an earlier version of the BIOS v207 carried an instruction 'Launch UEFI' in place of PXE Oprom line. The new BIOS v214 (which I haven't dared to touch yet) carries the following description on Asus site; "Disable CSM when Secure Boot is enabled". I've learned that the 'Launch CSM (Compatibility Support Mode)' is inserted in place of the former 'Launch UEFI' instruction. Does this imply that the three seemingly different options under the Boot Configuration tab are basically saying the same thing: you can choose between pure UEFI and a hybrid mode that is compatible with the classic BIOS? And what's the business about secure boot on a Windows 7 machine that isn't supposed to have it? I texted Asus support about this two days ago and have yet to hear anything from them.
     
  7. eidassan

    eidassan MDL Novice

    Jan 22, 2013
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    #7 eidassan, Jan 24, 2013
    Last edited: Jan 24, 2013
    (OP)
    Following my preceding post I'd like to walk you through what I think may result from three different lines of action:

    A: From Windows 7 disc 0 (with both discs connected) convert my disc 1 to gpt and install 2nd version of Win 7 (or Win 8 or even Vista). PROS: easy, fairly fail safe, Windows Boot Loader will automatically take care of dual boot screen configuration under UEFI. CONS: This isn't a 'true' dual boot, so when disc 0 dies the Windows install on disc 1 dies with it.

    B: With disc 0 disconnected install Win 7 (or 8 or Vista) on disc 1 using the pre-formatted mbr partitions and with boot info on the same disk. PROS: True dual boot, disk 0 dies and I'm up and running on disk 1 immediately. CONS: No user-friendly Grub, obligation to boot from BIOS override, rearranged partition letters (minor cosmetic nuisance). Also, risk that disc 1 doesn't see disc 0 or worse that Windows Uefi loader will somehow expropriate the boot info from the mbr disk and place it in its own EFI partition (unknown but probably doubtful). As further input, I tried to make an Acronis 11 backup (made on XP3 comp but supposedly UEFI-capable) and although disc booted successfully could not see disc 0 at all. But this might be an Acronis problem.

    C: Convert disc 1 to gpt AND disconnect disc 0 before installing Win 7 ( or 8 or Vista) onto disc 1 in UEFI mode. This should result in an EFI partition on each HDD. PROS: A coherent ideal solution with the best of both worlds. CONS: Potentially the worst of both worlds. As the EFI mode-for-all now allows everyone to see what everyone else is doing on the computer, a serious risk that EFI O will hijack EFI 1 boot, vice versa, or even that one or both installations will simply implode.

    I welcome your educated guesses regarding these scenarios or any better plan of attack.

    Also tnx, yeah, I'd be simply thrilled to hear a detailed solution if you manage to get XP3 up and running alongside Win 7 on a separate MBR disc. It's probably the most difficult combo of all. I was told flat out by my vendor that my Asus machine simply doesn't support it. But from some research I've found that apart from USB 3 drivers just about everything else should run albeit perhaps on crutches.

    Yes, but are those strictly data discs? I've the same. The real question is what if you hotswap a non GPT disk with another OS on it?
     
  8. tnx

    tnx MDL Expert

    Sep 2, 2008
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    #8 tnx, Jan 24, 2013
    Last edited: Jan 24, 2013
    Hi..

    Well I did try to install Windows XP but I suddenly remembered that it will not recognise the SATA pots.
    I could make a new XP disc with the Asus Sabertooth SATA drivers and test that at a later date but I dont have time right now.

    What I did do is.....

    Took all my drives out.
    Slung in a MBR HDD 80 gig.
    Loaded Windows 7 Ultimate x32 onto the drive. The drive is MBR. Windows worked perfectly. ( Loaded off a disc )
    I then slung my other two drives back in.
    My OS UEFI GPT drive and my storage GPT drive.
    Selected my UEFI as first boot,worked perfectly.
    Re-booted and selected MBR as first boot, worked perfectly...


    Both the installs are on completely seperate drives.
    Both installs were done with only that particular drive plugged in.

    My prefered method of dual booting is actually selecting the drive within the BIOS screen. Might take an extra minute or two but thats how I like it...

    I have taken some pics of the BIOS showing the drives including the drive with the UEFI icon on....

    I am definatly not David Bailey though....
     
  9. eidassan

    eidassan MDL Novice

    Jan 22, 2013
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    Ah really great tnx. Appreciate your effort in helping get to the bottom of this. So in fact you've tested my B) option and it apparently seems to work. What's not clear from your test is...can either disk perfectly read the others partitions? Naturally, each Win 7 version boots as C: off its respective disk but what about the rest. Also when both disks are installed, have you tried just letting the Windows Boot Loader do its thing without going into BIOS first? What happens then? As for XP, yeah, it's the classic SATA driver issue which I think one fixes by either a slipstream or pressing F6 at one point in the install and pointing the process to a USB key with the drivers loaded.

    I called Asus support three times, twice here in France, once in the U.S. Of the former, first I got a North African lady who sounded as she was coming in off a cocktail party who advised nothing more than: "Backup your data". LOL. The second French intervention came from a trilingual miss of Asian origin who told me flat out that she'd try and test the solutions at home when she gets off work. Nearly fell off my chair. And one wonders that China has put a man in space and has built the world's longest high speed train? In the U.S. I was rerouted to somewhere in Pakistan (amazing how far a dime will get you on a phone call these days). Anyway, after a half dozen holds to 'consult with my supervisor' (who was probably in Indiana) I was told simply in a robotic monotone: "Sir, Asus does not support dual booting its machines, we value our customers, have a nice day, etc." Isn't culture such a marvelous thing?

    Anyway, tnx I think we're nearly at the bottom of all this. And I'll have a go on my single machine this weekend.
     
  10. tnx

    tnx MDL Expert

    Sep 2, 2008
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    #10 tnx, Jan 25, 2013
    Last edited: Jan 25, 2013
    Hi..

    I think I know what your after. Your wanting to easily select which version of windows you want while at the boot screen by tapping up or down and pressing enter.
    This would make things easier for you.
    I only know how to set this up via EasyBCD, you did mention this APP. I personally do not like this method and sorry I am not wanting to install this on my working machine.

    What I will do though and this will sort things out. On my test rig which is running an Asus P8H61-MX.....

    I will install Windows 7 Ultimate x64 on UEFI.
    Then install on a seperate drive Windows 7 Ultimate x32 on MBR.

    I will test if both booot up properly by selecting each in turn as "FIRST BOOT"

    I will test if files can be swapped over from one drive to another. I dont see whay not to be honest.

    I will then install EasyBCD on to each windows and test if it is possible to to easily choose which ever version we want..

    As for Windows XP. Dont qoute me on this but I read that the BIOS SATA settings have to be set to IDE and not AHCI for XP to be installed. This would definatly put the spanner in the works.

    What I have just done.....

    Within my working Windows 7 I have converted an 160 GIG HHD to GPT using the "Disk MAnagement"
    I have formatted a USB stick to FAT32 and copied W7 Ult x64 files to it. I will alter the files so it will install as UEFI enabled.

    Sooooooo...

    Offf to do some testing.....

    Will report back ASAP.....
     
  11. tnx

    tnx MDL Expert

    Sep 2, 2008
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    Well...

    I am totally baffled.

    On my test rig I can install Windows 7 x64 on GPT UEFI.

    But once this is in I can not install Windows 7 x32.

    Not on seperate drives with each connected seperatly or even with both drives connected.

    mmmmmmmmmmmmmmm......Been messing for a good couple of hours now and got no where....

    I have not tried installing from a dvd yet. Dont actually have a spare optical drive. Might have to break down my working PC to get the dvd drive out......

    But sadly I have other things I need to do tonight....Will have to play,later or even tommorow,,,,


    Puzzled ????????????????
     
  12. tnx

    tnx MDL Expert

    Sep 2, 2008
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    Yeppp....I know this....I was testing to see if I could get GPT and MBR to dual boot..

    I had W7 x64 UEFI on GPT and W7 x32 on MBR drives.....

    Thought I had it sorted but not so...
     
  13. tnx

    tnx MDL Expert

    Sep 2, 2008
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    Well....

    Update...

    First I installed Windows 7 x32 off a disc onto MBR HHD. Worked perfectly.

    Second. I installed Windows 7 x64 UEFI on a GPT HDD. Worked perfectly.

    Third. With both drives connected I can select which version to boot into via the BIOS. Each works perfectly.

    I then downloaded EasyBCD 2.2 and placed it on the x64 version. Installed.

    I then booted up into x32 and succesfully copied the .exe from the x64 GPT HDD to the x32 MBR HDD.

    Having installed EasyBCD 2.2 onto both drives and changed some settings. PLEASE NOTE I HAVE ONLY USED THIS APP A FEW TIMES !!!!

    I was able to add both versions to the boot screen.
    I was able to see both versions but I was unable to select x32 only the x64 version...

    I put this down to the EasyBCD settings...i am not sure. This needs more work with the app..

    But this proofs both UEFI\GPT and MBR installs can be done,on different drives of course. Files can be transfered from one to the other with no problems.

    Hope this helps.....
     
  14. tnx

    tnx MDL Expert

    Sep 2, 2008
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    Well...

    Update...And conclusion...

    With both drives connected. EasyBCD 2.2 installed.
    I set the BIOS so the x32 MBR HDD was set to first boot and the default boot drive I was able to see both versions at the boot screen and I was able to select either just by tapping up or down and presssing enter. No more going into the BIOS.

    I would say this is a good result and proofs it does work and works well.

    If infact this is what you want or need to do.....

    To point out. Within EasyBCD I named the version x32 and x64 so they are easily and quicky selected....

    Hope this helps...

    This has been very fun to do and I'm glad I came along for the ride....Right up my street...

    :D

    Thanks...
     
  15. eidassan

    eidassan MDL Novice

    Jan 22, 2013
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    Brilliant, tnx, just brilliant. I'll have you know that to my mind this specific setup hasn't previously been verified by anyone on any of the forums I've been connected to over the past couple of weeks. There remains the niggling question as to why when you installed via UEFI first the Legacy install wouldn't take. This is a bit of a bugger. Also your experience seems to imply that if the BIOS is set to boot off the MBR disc first then EasyBCD will allow either disk to boot whereas if the GPT disk is set to boot first (BIOS-wise) then EasyBCD will only let the UEFI disk boot. I wonder if this depends on what's going on within EasyBCD. Didn't I read somewhere that EasyBCD should only be on one disk, notably the last one installed? You also say you copied the exe file from one to the other. Is this same as installing on the other disk? To me the fundamental question is where is the information stored that EasyBCD uses. I ask this having never even used it myself. It must be on one of the disks, obviously, and depending upon where the dual boot info is, will execute things or not. I even wonder if somewhere along the line boot files have been overwritten somewhere.

    Can you still 'manually' boot either disk off the BIOS? One interesting test would be to remove the x32 disk and see if the 64 bit EFI install will still boot automatically. Also, when you set the x64 EFI 'to boot first in the BIOS' what was being prioritized: disk 0, disk 1 OR Windows Boot Loader? I'd be curious to know whether if Windows Boot Loader is allowed to kick in off the 64bit install that this would make a big mess of things. But again I'm just babbling in the woods, again. I've got enough encouragement now to do my own test, this time with two versions of x64. Anywhere, thanks so much for your efforts in getting into this new territory. And I'll be sure myself to report back on my own experience.
     
  16. sebus

    sebus MDL Guru

    Jul 23, 2008
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  17. tnx

    tnx MDL Expert

    Sep 2, 2008
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    # eidassan

    Copying the .exe file is not the same as installing it....I did infact install onto both drives.
    I personally do not like the app and I dont like setting up a dual boot in this way.

    I have done the test of unplugging x32 drive,this automaticly set the x64 UEFI drive to first boot.
    And this is why I dont like this method.
    When the machine booted it still gave me the choice of selecting x64 or x32....

    However x64 booted up properly and is running as I type. I know I could easily delete the x32 from the boot record via EasyBCD.......

    I have been thinking about XP and W7 x64 and whether I could get a dual boot with these two.
    I think if the SATA controller was set to IDE Windows XP would install its whether Windows 7 x64 could be installed on a GPT drive or not..I think not,but dont quote me on that.

    I suppose there is only one way to find out....


    If it was me I honestly would do away and forget all about the boot screen choice and phisicly select the version to boot from BIOS. Some boards are F12 I think. On my Asus boards I just press DELETE,enter the BIOS,I do NOT change the BOOT prioraty but just slect the quick boot option if I wish to boot another drive other than my main OS one.
    Simple effective and no messy apps to worry about.

    Anyway...Good luck with your own tests and DO get back to us with any results..

    :biggrin:
     
  18. eidassan

    eidassan MDL Novice

    Jan 22, 2013
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    Absolutely agree, tnx, when I found the way the one-time boot function works (I, too, have an Asus) I find it just as simple to use as the EasyBCD interface. It's clearly more accurate to boot (no pun intended). Easy BCD can be prone to false-positive errors especially if the user configures it wrongly. I've seen this problem with others on various web sites. Sticking with the BIOS is straight and to the point, and you have one less intermediary where things can go afoul.