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Windows 7: Dual Boot 7 32bit and 64bit under Uefi

06 Jan 2013   #1

windows home premium 64
 
 
Dual Boot 7 32bit and 64bit under Uefi

Ok, this has been dealt with in various places but not to my total satisfaction. So bear with me if the answer is hidden somewhere in the forum.

I've got an oem asus with 2 hdds the first of which has Win 7 64 home pre-installed via uefi boot manager. It is a gpt formatted disk. The second disk is empty and is set up with mbr. I wish to dual boot onto the second disk with Win 7 32 Pro but fear a rejection due to the fact appparenly Uefi will not manage 32 bit installs/boots. More to the point , will the mbr variance on the 2nd disk somehow make for an exception to this 32bit 'prejudice' on the part of uefi or simply make matters worse? My bios has a single option regarding a legacy setting connected with uefi which is disabled. PxO... or rather. Gregrocker seems to think obviating the problem with 2 physically separate installs (i.e. Hdd disconnect) will allow a Bios based boot as opposed to a Uefi/Windows managed one. Is this workaround a sure thing and my only option or is there a practical way to go the classic route with the auto boot loader screen on start up? Perhaps a better way to put it is..on dual boot systems is it true that you can't have BOTH uefi and the bios directing the show. You gotta choose one or the other. Frankly, to my novice mind this whole problem seems to be a regression from the XP days. Anyway, a definitive answer from you all would be more than welcome. Thanks loads.

My System SpecsSystem Spec
06 Jan 2013   #2

Microsoft Community Contributor Award Recipient

ME/XP/Vista/Win7
 
 

Quote   Quote: Originally Posted by sadiesan
Gregrocker seems to think obviating the problem with 2 physically separate installs (i.e. Hdd disconnect) will allow a Bios based boot as opposed to a Uefi/Windows managed one. Is this workaround a sure thing and my only option
Can you post a link to Gregrocker post.

Why would need to install x32?
My System SpecsSystem Spec
07 Jan 2013   #3

windows home premium 64
 
 

@ theog

Which post and how? Dual boot in order to have a backup system ready to go should the first one tank (been there, done that). Secondly, for the odd app that won't run, or run poorly, on 64bit (my oem home edition is w/o XP emulation.). And a possible third reason would be to dedicate the 2nd disk as a non-internet exposed volume for video editing.

@ gregrocker

Thanks for the feedback, greg. So why then after all is it seemingly possible to do my dual boot off the uefi partition? I ask this since in at least two other threads this posed a problem. Is it because my 2nd disk is mbr? I admit I don't quite get the full picture as to what is going on 'inside' upon startup and how uefi and mbr disks inter-relate under a windows managed dual boot scenario. I suppose my confusion stems from the notion that to dual boot you must either go the uefi route with two uefi disks, or the mbr way with two mbr disks. Is this untrue and you can in fact mismatch?

Overnight I rethought the matter and it seems from a hardware security perspective your 'unlinked' separate installs method is probably the more sure one. Which makes me ask what then will happen to the various volume designations? Won't I have two C: drives (since the 2nd OS won't be 'seeing' the disconnected first one)? And won't this skewer the volume names left and right depending upon which OS is booting? Thanks again.
My System SpecsSystem Spec
.


07 Jan 2013   #4

Microsoft Community Contributor Award Recipient

ME/XP/Vista/Win7
 
 

This is the second time you have quoted Gregroker with no source.

source
Dual Boot 7 32bit and 64bit under Uefi

Quote   Quote: Originally Posted by sadiesan
I ask this since in at least two other threads this posed a problem.
source

Dual Boot 7 32bit and 64bit under Uefi

Quote   Quote: Originally Posted by sadiesan
Gregrocker seems to think obviating the problem with 2 physically separate installs (i.e. Hdd disconnect) will allow a Bios based boot as opposed to a Uefi/Windows managed one. Is this workaround a sure thing and my only option

source
Dual Boot 7 32bit and 64bit under Uefi

Quote   Quote: Originally Posted by sadiesan
@ theog

Which post and how? Dual boot in order to have a backup system ready to go should the first one tank (been there, done that). Secondly, for the odd app that won't run, or run poorly, on 64bit (my oem home edition is w/o XP emulation.). And a possible third reason would be to dedicate the 2nd disk as a non-internet exposed volume for video editing.
You will need two Product license keys.
My System SpecsSystem Spec
07 Jan 2013   #5
Microsoft MVP

 

There is much to still discover with UEFI as it is new, specific to each mobo, and challenges much of what we have learned here in four years time. The principle of keeping OS's on independently bootable HD's has worked best overall for normal MBR installs, but whether this works generally to Dual Boot GPT/UEFI to dual boot with MBR needs more results. Have you tried it? Can you reference the threads where this has failed?
My System SpecsSystem Spec
10 Jan 2013   #6

windows home premium 64
 
 

@Gregrocker

Thanks, Greg. Sorry for delay in getting back. Your answer pretty well sums up in content and tone what I was looking for.. I will go ahead and separate the two systems entirely. I am somewhat taken aback that my enquiry proves not to be as naive as I'd have thought. I'd really have thought that the windows community would have a pat solution for this issue by now. Live and learn. I'll let you all know if anything revolutionary comes out of o my installation this weekend.

@theog

Ok, I see what you mean. In truth I thought you were referring to a sort of forwarding of my post to one of Greg's!? No, I didn't, and rarely do, go to the bother of copy-pasting left and right in the context of a general intro cha for which there was no single source quote that merited citing. Otherwise there'd be dozens of sources to bring into the equation and I think such a lengthy bibliographic recital would only tax the patience of you all more than it would inform. There was a single thread by someone of the name of Marilyn that was never resolved that had some bearing on my issue, but I wouldn't know what to quote anyway. As for linking to Gregrocker's suggestion, why bother? There was no issue to grind nor hairs to split, he reconfirmed a simple common sense suggestion that he's mentioned in the past and I validated it as the better of my options. End of story. Not to pick a fight or anything, but there are times when regurgitated text is superfluous.

Anyway, thanks all and I'll be checking in from time and again to see if anyone's got a thesis as to how uefi and mbr ought to get along with one another under the same roof. All the best and until my next crisis.....Sadie
My System SpecsSystem Spec
10 Jan 2013   #7
Microsoft MVP

 

Please let us know what works for you.
My System SpecsSystem Spec
15 Jan 2013   #8

windows home premium 64
 
 

After a few days in snow country and a trip to the vendor of my new asus machine, I'm forced to come back here to square A again. I apparently had overlooked that if I touch either of my hdds (i.e. remove them) it will nullify the two year guarantee on the entire computer. Not a good choice.

Sooo, it led to me to think of a compromise solution that is neither the physically separate dual boot that Greg has recommended, but is possibly also not one dependent on the uefi windows boot loader either.

On a test run, having got the 2nd Win 7 boot install on to a USB stick, the one-time BIOS override screen gave me the new option of booting from either UEFI: Sandisk or just Sandisk. Am I wrong or is my BIOS inviting me to either A) setup my 2nd Win 7 install on disk 1 by modifying the EFI partition on disk 0 in order to reflect a dual boot in windows boot loader, or B) set up my 2nd Win 7 install 'directly' on the mbr partition as it exists on disk 1 and thus 'bypass' the disc 0 EFI partition entirely? The B) route would then necessitate a manual BIOS mbr boot each time from the one-time boot screen. On the other hand, if I go the A) route what will happen to that destination mbr partition on disc 1? Will I be prompted to convert it to gpt or perhaps will even a 2nd EFI boot partition be created?

I know this all sounds rather confused and contorted and rehashes a similar question from my earlier post regarding the co-existence of gpt and mbr. I should maybe just do it and see what spits out. Yet whatever I do, I do want the assurance that my original 200mb EFI partition will neither be erased nor irretrievably modified.

Thanks again guys.
My System SpecsSystem Spec
15 Jan 2013   #9
Microsoft MVP

 

I'd just do the standard Dual Boot with the other HD attached which will auto-configure the Dual Boot menu for you.

Keep it in UEFI mode follow the special steps required for UEFI (Unified Extensible Firmware Interface) - Install Windows 7 with - Windows 7 Forums.

There are also special steps required to format the flash stick installer: UEFI Bootable USB Flash Drive - Create in Windows

If you have any problems our resident UEFI expert Theog should be around in the morning.
My System SpecsSystem Spec
16 Jan 2013   #10

windows home premium 64
 
 

After another long day back to this thread. Greg, your 'easy' approach to just do it all through the Windows 7 Boot Loader is really just a second option. We'd agreed that ideally the two OS should have as little influence upon one another as possible. Meaning if one disk dies the other would become operational right away, which would not be the case using the full EFI driven Windows approach. I found a quote (Theog will be happy) from the Microsoft Community site that closely touches on what I was getting at earlier. It's about 10 months old.

Quote:
I believe I understand what happened in my case. Someone on the ASUS forum said something that caused a light bulb to go off. I'm pretty sure that when I installed Windows 7 on this system, I did it in BIOS mode, not UEFI mode, so that's why Windows 7 made MBR partitions I guess. I didn't realize that, at least for ASUS, you turn UEFI mode on by picking a boot device that has UEFI enabled rather than one that doesn't. It was only fairly recently that I noticed that some of the boot devices were marked as UEFI devices. Anyway, then later when I tried installing Windows 8 CP, I booted from the UEFI DVD device (by then I had noticed the difference), and that's why Windows 8 didn't like my MBR partitions. Today, I booted from the non-UEFI DVD device into Window 8 CP setup, and it installed on my MBR partition just fine. So, if you have a UEFI system, make sure you understand whether you are booting in UEFI mode or not.
The difference being that I'm on an OEM system of Win 7 installed in EFI mode on a GPT disk with a second unused MBR disc and I'm installing the second with 32bit Win 7 (or in a pinch Vista or XP3). By the way doesn't EFI mode reject 32 bit installs from the get go anyway?

So does the above citation have any bearing on my problem. Can I confidently get my 2nd Win OS to install on the MBR disk and not have my Win 7 EFI install have a fit or render itself unoperational? Would I get two OS operating out of their respective C: drives that would see and talk to one another yet not try hijack each other? If it helps the comp is an Asus N76VM and my bios is American Megatrends v211 with Aptio. Also would i still need to scrupulously adhere to the following links which seem primarily geared to a single OS install UEFI (Unified Extensible Firmware Interface) - Install Windows 7 with and UEFI Bootable USB Flash Drive - Create in Windows One of these tutorials would seem to setup a second EFI partition on the 2nd disk. Or am I wrong? Thanks mucho much.


My System SpecsSystem Spec
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