Installing a MacOS (Catalina) after running Windows 10

[tillytoon]

Hi, I've been running into problems installing a MacOS on my system after running Windows 10 first.

My build was done for the purpose of running a MacOS, but I also purchased Windows 10 with the intention of making a dual boot system with two M.2 drives (one for each OS). Windows 10 was installed first and I ran it, assuming I would be able to choose the other empty M.2 drive in the boot options of my BIOS settings to install a MacOS. After running into problems installing a MacOS, I removed the M.2 drive with Windows 10 installed on it, as I was told the system wouldn't recognize Windows 10 once the drive it was installed on is removed. Unfortunately, Windows 10 is still listed under boot options as 'other OS' in my BIOS settings after the drive Windows was installed on was removed.

I'm wondering if there is a way to install a MacOS on a separate hard drive after running Windows on that system? I've read online that the product key is stored on the motherboard and I'm concerned that I'll have to replace the motherboard in order to successfully install a MacOS.

I've attached images of my 'boot options' in BIOS and of what I read about the product key encryption on the motherboard.

Any input would be very appreciated, I've been dealing with this issue for a long time.
Thanks so much!

Motherboard:
Gigabyte Z390 Aorus Elite

CPU:
Intel Core i7 i7-9700K

Graphics card:
RX 580

SSD (x2) (1 removed atm)
Crucial 1TB Solid State Drive - PCI Express - Internal - M.2 2280

Ram (x2)
Corsair 16gb

Cooler
Cosair H115 Ipro CPU cooler

Power supply
EVGA SuperNOVA 650W

 

[Going Bald]

Put the Win10 drive back in the slot. The only reason for removing it is to make sure you do not accidently format it for Mac OS.
When first installing, since you have 2 slots, did you make sure the Win10 was in the first slot the BIOS looks at for a boot drive?

 

[tillytoon]

That's helpful to know. I got the impression that the presence of Win10 would prevent MacOS installation, but it's a relief to hear that's not the case.

When I installed Win10 I didn't know that it should be in the first slot the BIOS looks at, but it was installed on the M2A drive, which must be the first one the BIOS looks at for a boot drive (the image attached of the M.2 slot info was taken while the drive with Win10 installed on it was removed, but it was in the M2A slot).

I've understood that the boot option priorities are important to the installation process, but I can't find a way or any directions on how to change boot option priorities in the BIOS manually. I'm going to try switching the placement of the the M.2 drives (putting them in the other slots) to try to install MacOS in the M2A slot, since I haven't been able to install MacOS' on the M.2 drive in the M2M slot. That's the only way I can think of to assist the installation of MacOS by giving its drive first booting priority.

Hopefully that will make a difference. If it doesn't matter please let me know, otherwise I'll reply to this again after I've swapped the drives and tried it out.

 

[Going Bald]

Do you have any drives/devices connected to the SATA ports? Some M.2 slots are disabled if SATA ports are used and vice versa. If you have both M.2 slots occupied do both show up as boot options in the BIOS?

 

[tillytoon]

The images in my last post of the boot options in the BIOS were taken while both M.2 slots were occupied. I thought that the M2M slot wasn't showing up as a boot option because there is no OS installed on that drive, but maybe it's because there's a SATA port(s) being used by another device?

This is my first build and (because I'm so new at this) I brought it into a shop to complete the second half of the build, so I can't think of what else might be connected to the SATA ports. My mobo has 6 of them, which is enough for what I need. Are M.2 slots sometimes disabled because they operate through serial processing are connected in the wrong order? I'm just trying to understand why the second M.2 slot (M2M) doesn't show up as a boot option even though it's recognized under 'M.2 slot info'.

I haven't noticed any indications about SATA connections in the BIOS, but I need both M.2 slots to be available for dual boot options, so maybe I'll bring it into a shop to see if I can get some help with that. I'm going to just swap the drives between the two M.2 slots in the meantime, since installing MacOS on the 1st priority slot is my main goal right now.

 

[Going Bald]

The images in my last post of the boot options in the BIOS were taken while both M.2 slots were occupied. I thought that the M2M slot wasn't showing up as a boot option because there is no OS installed on that drive, but maybe it's because there's a SATA port(s) being used by another device?

This is my first build and (because I'm so new at this) I brought it into a shop to complete the second half of the build, so I can't think of what else might be connected to the SATA ports. My mobo has 6 of them, which is enough for what I need. Are M.2 slots sometimes disabled because they operate through serial processing are connected in the wrong order? I'm just trying to understand why the second M.2 slot (M2M) doesn't show up as a boot option even though it's recognized under 'M.2 slot info'.

I haven't noticed any indications about SATA connections in the BIOS, but I need both M.2 slots to be available for dual boot options, so maybe I'll bring it into a shop to see if I can get some help with that. I'm going to just swap the drives between the two M.2 slots in the meantime, since installing MacOS on the 1st priority slot is my main goal right now.

Your board has restrictions on what SATA lanes are available when Drives are connected to the M.2 slots. It also depends on the TYPE of M.2 capable drive. From your board manual: