"MBR Error 1 - Boot from floppy" after clean reinstall

"MBR Error 1 - Boot from floppy" after clean 8.1 reinstall

I had previously posted about boot problems with a cloned SSD, which are described in the first post at http://www.eightforums.com/installation-setup/66457-cloned-drive-wont-boot.html. Before I get into more, I suspect this is a hardware issue, either the motherboard (Gigabyte GA-Z97X-UD5H) or the Samsung 850 Pro I got shortly after the mobo. However, for the moment, I want to make sure it's not a Windows issue. Ok...

Earlier this month, I wiped the SSD and did a clean reinstall of Win 8.1 Pro x64, this time using UEFI. Right away, three of the first six boots started with the MBR Error 1 message on first try, then rebooted fine with ctrl-alt-delete (I've seen none of the other boot errors from before). Then the error pretty much went away except occasionally. Now it's back with a vengeance. Just as before the reinstall, when I open BIOS sometimes it shows the system drive and sometimes it doesn't, then all of a sudden it does, and sooner or later starts normally. Along the way, BIOS sometimes shows a different boot order that has to be readjusted. Sometimes at one point the Windows repair screen comes up, but repair fails. One time I tried a recovery repair from a USB stick (unsuccessful), and after that I ended up with another entry in BIOS for the Samsung drive called "Windows Boot Manager Samsung..." What's that?. It's confusing because sometimes that entry shows, sometimes the UEFI Samsung entry shows, sometimes both, but ultimately successful startup doesn't seem to depend on which is present or chosen. In any case, I was just using Diskpart (USB stick) to start a BCD repair, but realized I don't know which is the boot partition (to give a drive letter to). See the drive screenshot. Thanks,

I see that Disk 2 is MBR was that your old boot OS Drive? you might want to disconnect it and see if booting is a little smoother

Quick reply:
1) No, Disk 2 is not the old OS. The latter was another not currently connected SSD.
2) In the old thread, which I wouldn't expect anyone to read past the first post, if that, I disconnected all the other HDDs and it had no effect on boot problem. No reason why it would now.

My question remains which is the partition, presumably the boot partition, to select with Diskpart (see the screenshot)?

Are you trying to use the bcdboot X:\windows command?

How to use the BCDboot command in Windows 8/10. -> link

The question is which is the EFI partition.

Duh... Not sure if I missed it or couldn't believe the FAT32 volume was it. Thanks. Will see if the fix worked (only a sample of one so far).

Next question: As I mentioned, after the attempted repair from the recovery stick, BIOS > Peripherals started showing the following entry:
"Windows Boot Manager (PO: Samsung SSD 850 Pro 256 GB)"

What is that? And what is the difference between that and the original reinstall entry that reads something like "UEFI Samsung ....," which was initially there all the time but since WBM showed up has appeared sometimes and sometimes not?

Here is an example of the Asus motherboard boot menu.



Gigabyte motherboard with UEFI firmware. How to install Windows 8/10 64-bit in UEFI Boot Mode. -> link

Thank you for the screenshot and link and the work you've put in creating the instructions (I did already had those settings). The thing is they don't answer my question(s):
- What is Windows Boot Manager?
- How does it differ from the UEFI: Samsung SSD entry?
- Why did it show up only after I tried to run repair from a recovery USB stick? (before that there was only UEFI: Samsung SSD entry)
- Why has the UEFI: Samsung SSD entry largely disappeared from BIOS boot options, showing up only occasionally?

Thanks,