Question HDD with MBR partitioned OS not detecting a secondary GPT SSD OS?

Dec 14, 2022
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Hi , so i bought a 512gb nvme m.2 ssd and after removing my old hdd , i installed windows 10 on it with only one drive and partitioned it GPT . so after that i reconnected my old hdd which is mbr and has windows 7 on it .
if i choose my boot option to ssd , win 10 recognizes my hdd but if i change boot to hdd , win 7 won't recognize my ssd .
so my Question is : is it normal ?
Does it damage ssd or the os on it ?
Should i remove my ssd when i want to use my win 7 ?
I am going to migrate to win 10 but my old windows has so many things and i have to come back to it once in a while until i move everything .
what should i do ?

Thank you .
 
The motherboards I've used have the option in BIOS (well, it isn't actually a BIOS anymore,it is a UEFI) to pick (A) old style BIOS support only, (B) UEFI support only, or (C) UEFI or BIOS (hybrid) support. You'd need to select the latter.

The BIOS or UEFI is responsible for initial setup of your motherboard, e.g., power rails and clocks. Old style BIOS also has an understanding of legacy MBR style partitioning, while UEFI has an understanding of GPT style partitioning. If the BIOS is told to go in one mode or the other, then you are telling it to forget how to work with the opposite mode. See if you have a mode for supporting both legacy MBR and UEFI.

Note that the o/s itself must also support whichever mode is involved. I'm not sure, but I don't think Windows 7 can boot from UEFI, but perhaps it can read UEFI if the updates are complete (someone else might comment on whether an updated Windows 7 normally works, non-boot, with UEFI, on a motherboard with dual support for both MBR BIOS and UEFI).

Incidentally, old style MBR BIOS partitioning has more limitations on size which could result in only part of an MBR large disk being recognized, but fully accessible if instead it is UEFI.
 
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Dec 14, 2022
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The motherboards I've used have the option in BIOS (well, it isn't actually a BIOS anymore,it is a UEFI) to pick (A) old style BIOS support only, (B) UEFI support only, or (C) UEFI or BIOS (hybrid) support. You'd need to select the latter.

The BIOS or UEFI is responsible for initial setup of your motherboard, e.g., power rails and clocks. Old style BIOS also has an understanding of legacy MBR style partitioning, while UEFI has an understanding of GPT style partitioning. If the BIOS is told to go in one mode or the other, then you are telling it to forget how to work with the opposite mode. See if you have a mode for supporting both legacy MBR and UEFI.

Note that the o/s itself must also support whichever mode is involved. I'm not sure, but I don't think Windows 7 can boot from UEFI, but perhaps it can read UEFI if the updates are complete (someone else might comment on whether an updated Windows 7 normally works, non-boot, with UEFI, on a motherboard with dual support for both MBR BIOS and UEFI).

Incidentally, old style MBR BIOS partitioning has more limitations on size which could result in only part of an MBR large disk being recognized, but fully accessible if instead it is UEFI.
Thank you for your help ,
so based on what you said i have to make some changes in uefi to recognize my ssd . but what if i don't need the ssd to show up when using win 7 ? i will eventually migrate to win 10 / gpt for good but i need the old os for like one more month .
will not being able to read or understand the drive by os/motherboard harm my drives ?
my motherboard is gigabyte b150 hd3 .
 
Dec 14, 2022
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yes, this is normal, windows 7 doesnt have nvme drivers on its own
https://support.microsoft.com/en-us/topic/update-to-add-native-driver-support-in-nvm-express-in-windows-7-and-windows-server-2008-r2-03cd423b-d42e-66c2-722b-019d16455a6b
inside you can apply for hotfix which you will receive through email
Thank you for your help .

what if i don't need the ssd to show up when using win 7 ? i will eventually migrate to win 10 / gpt for good but i need the old os for like one more month .
will not being able to read or understand the drive by os/motherboard harm my drives ?
 
Thank you for your help ,
so based on what you said i have to make some changes in uefi to recognize my ssd . but what if i don't need the ssd to show up when using win 7 ? i will eventually migrate to win 10 / gpt for good but i need the old os for like one more month .
will not being able to read or understand the drive by os/motherboard harm my drives ?
my motherboard is gigabyte b150 hd3 .
Yes, if your BIOS supports both legacy MBR and UEFI, then setting it to that mode would allow the drive to be recognized. There is of course also a requirement for the operating system to understand both modes if you want to mix them. I think Win 7 was purely legacy BIOS mode, and I'm not sure if it can use a UEFI drive (I know it cannot boot to a UEFI drive, but possibly it could use the drive once booted if it is patched to the most recent release...not sure of Win 7). Options related to seeing drives and partitions in the BIOS do require setting to the UEFI or legacy mode (or both) to see those drives.

UEFI partitions have what is called a "protective MBR" in it. This is the "master boot record", and in UEFI, it is fake. What it does though is to cause legacy BIOS software to not mess with the drive (you might be able to intentionally mess with it, but you'd have to try). UEFI is quite aware of legacy BIOS MBR. So it won't hurt to mix them even though it might also be without purpose.
 
Yes, if your BIOS supports both legacy MBR and UEFI, then setting it to that mode would allow the drive to be recognized. There is of course also a requirement for the operating system to understand both modes if you want to mix them. I think Win 7 was purely legacy BIOS mode, and I'm not sure if it can use a UEFI drive (I know it cannot boot to a UEFI drive, but possibly it could use the drive once booted if it is patched to the most recent release...not sure of Win 7). Options related to seeing drives and partitions in the BIOS do require setting to the UEFI or legacy mode (or both) to see those drives.

UEFI partitions have what is called a "protective MBR" in it. This is the "master boot record", and in UEFI, it is fake. What it does though is to cause legacy BIOS software to not mess with the drive (you might be able to intentionally mess with it, but you'd have to try). UEFI is quite aware of legacy BIOS MBR. So it won't hurt to mix them even though it might also be without purpose.
im pretty sure youre just confusing him

  1. he doesnt have issue with MBR/GPT vs old bios vs UEFI, as he can boot from nvme already
  2. win 7 can see GPT drives and can be also installed on them
  3. win 7 cant see nvme drives because it does not have nvme drivers
without driver only sata drives will show up

for OP, no harm to nvme device if youre running win 7 without nvme driver
 
im pretty sure youre just confusing him

  1. he doesnt have issue with MBR/GPT vs old bios vs UEFI, as he can boot from nvme already
  2. win 7 can see GPT drives and can be also installed on them
  3. win 7 cant see nvme drives because it does not have nvme drivers
without driver only sata drives will show up

for OP, no harm to nvme device if youre running win 7 without nvme driver
You are probably right, and I should clarify something: Not seeing a drive and not seeing partitions could be related, but are not the same.

One needs a driver for a device before the device can be seen. If the drive does not have a driver, it is invisible. A BIOS itself, and boot software, must have drivers to see devices (many people overlook this). Then the operating system itself also needs a driver for the device. Once the device is detected, for drives, then another driver is required for seeing partitions on that drive. It is possible to see a drive without seeing the partitions; it is not possible to see the partitions without seeing the drive. It is a chain of dependencies, and those dependencies occur at every stage of boot, including the BIOS and bootloader if booting off of that device.

A lot of what I was looking at revolved around the step in the original post where the old drive is added back in and the BIOS was used to switch to booting to it, but it failed. It was windows 7, and not the BIOS which wasn't recognizing the drive, but I mistakenly missed the fact that it was still booting successfully to the old drive (versus booting to win 7 on the SSD, which is not what it was doing). Restated, the BIOS is not having any issue booting to either drive, and the BIOS is having no issue finding partitions on either drive; only win 7 is having issues, and only with the SSD, which is of NVMe format and not SATA. So you are correct, it is a missing driver in win 7 for NVMe drives.

The original idea that there is no danger to either o/s destroying the other by having both drives is correct under either scheme without regard to whether it is missing an ability to use various partition schemes versus missing drive type itself. There is nothing to worry about.
 
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