Win 10 dual boot on a GPT disk

[jbraner]

Hi,

I've been using BIBM for a long time - booting two Windows partitions (one is always hidden when the other one boots) from a MBR SSD drive.

I've got a new NVMe drive and I'm trying it out as a GPT drive (if I can't get it to work I'll just go back to MBR).
I'm just a little stuck with some terminology.

I assume I'll just have to get BootIt UEFI - that's no problem.

Do I build a Windows boot loader on the new disk?
If so - would both partitions use the same boot loader (one at a time) - or do they each get one?
In other words - thi sis on it's own little 100MB partition isn't it? So can each Windows partition use it - thinking they're the only one using it?
(each Windows 10 install will think it's the only system disk - there are other data disks that both share)
Or will BootIt UEFI provide a boot loader - and the I just boot my Windows partitions using that?

I'm not even sure how the current MBR actually works. But it works fine.

I'll continue to experiment - and will buy BootIt UEFI - but any help is appreciated.
I've got some articles about how to "fix" boot loader (that was never there) - bu tjust want to have abetter idea what I'm doing.

Thanks.

[jbraner]

Or should I just forget it - and make it a MBR disk?

[DrTeeth]

On Sat, 10 Oct 2020 09:58:58 PDT, just as I was about to take a herb,
jbraner disturbed my reverie and wrote:

>Or should I just forget it - and make it a MBR disk?

I have decided to stay with MBR disks myself. UEFI does not bring
anything useful to the table for me at all. Others, strongly disagree.
--
Cheers,

DrT

** Amateurs built the Ark, but professionals built the Titanic.**

[Brian K]

John,

Does your motherboard support booting an OS in MBR mode on a NVMe PCIe M.2 SSD?

[jbraner]

Brian K wrote:
> John,
>
> Does your motherboard support booting an OS in MBR mode on a NVMe PCIe M.2
> SSD?

Good question!
I haven't got that far
I'm going to try setting it up as a GPT dual boot first. if that fails I'll try booting it as MBR (I just assumed that would work).
The NVMe drive appeared in the BIOS boot list when it was formatted as MBR - so I'm assuming it would work that way. It's not listed in any documentation - but the motherboard (and BIOS rev) is very new - and seems to cover most bases.

I have a little more RTFM to do and will attack this tomorrow

Reading the BootIt UEFI manual - it looks like you can set the one GPT boot area for multiple boot devices - which is probably what I'll want to do (rather than each of the Windows partitions thinking the one boot loader is "mine".

I have the luxury of playing around with this without (hopefully) screwing up the working partions on their own SSD drive.
That's why I thought maybe I'll try running it as a GPT disk, while I'm in the process of changing over. Otherwise if I leave it as MBR - I won't touch it for another 7-8 years

When everything is all set up - all I have to do is clone the "working" partitions to the new NVMe drive - so they're up to date

[Brian K]

John,

I misunderstood. I thought you were going to try MBR. GPT will be fine.

Leave your NVMe blank and install BIU. This will give you two partitions.

ESP 400 MiB
MSR 16 MiB

Now install Win10 as per page 59 in the BIU User Manual.

If you want a second Win10, copy the partition in Partition Work but remember to select "Add to Boot Menu".

[jbraner]

Hi Brian,

I wish I'd seen this earlier

I wasted 5-6 hours today trying to get just one partition to boot - without any luck.
I got some info online and created the EIF partitions manually - but couldn't get the copied Windows partition to boot.

I will buy Boot It UEFI right now, wipe the disk and start again.
I've been using BIBM.

The thing is - the copied partition is used to booting from its current MBR disk.

I'll read through the BIU manual. If it's going to create those partitions for me - hopefully it will help me with the bcdedit etc.

You've given me hope!

PS I couldn't get it to boot from making the NVMe a MBR disk either. It's been a long day

[jbraner]

Also, I'm assuming my MBR disks will still boot after installing BIU (until I get everything swith ed over)...

[Brian K]

I though you wanted a UEFI system. Prior to installing BIU you must make changes in the UEFI BIOS. Disable CSM, set to boot from Win10 and enable Secure Boot.

Any OS on MBR disks won't boot. You can't mix OS. Prior to installing BIU I'd disconnect all GPT drives except for the NVMe SSD. This stops BIU from being installed on the wrong drive.

[jbraner]

Oh well, I'm screwed then.
I don't want a UEFI system - I want a mixed system.

I can make it a UEFI system, but I'll have to think it through better - and I won't have my current disk to boot from if it doesn't work.

Oh well, I've got my BIU, so it's there when I'm "ready"

I just tried seting up the NVMe disk as MBR to see if it would work - but that's not working either
So - back to the drawing board


Thanks for your help anyway Brian.