Installing macOS on new disk

[dantown]

Hello there! I'm really new into iMacs or Apple devices. I got an iMac mid 2011 21.5" from the trash (literally) since about a year. It's working nice, it has a 256GB SSD disk, 6GB of RAM, AMD Radeon HD 6770M. But, I started to notice that most common apps are not working anymore under High Sierra (the latest OS supported on this model) and I'm tempted on updating upto Big Sur using OCLP.

As the iMac is working good for now, i'm afraid to make any mistake and damage something.

So, i was wondering... Can I put a new (blank) SSD disk, install BigSur on it, and if anything goes wrong, put the old disk back and continue using the iMac without doing anythen else? Or installing a new disk/OS will render the older disk not usable to boot my previous installation? Don' know if I explained it well.

Thanks to anyone who can help me with info or tips of some sort.

 

[hermannkm]

Should work without problems. You could also use an external disk or USB stick just for testing. Using OCLP myself on a MacBook Pro from 2012 (Ventura, no sound) and a MBP late 2013 (Sonoma, everything working).

 

[Nguyen Duc Hieu]

Hello there! I'm really new into iMacs or Apple devices. I got an iMac mid 2011 21.5" from the trash (literally) since about a year. It's working nice, it has a 256GB SSD disk, 6GB of RAM, AMD Radeon HD 6770M. But, I started to notice that most common apps are not working anymore under High Sierra (the latest OS supported on this model) and I'm tempted on updating upto Big Sur using OCLP.

As the iMac is working good for now, i'm afraid to make any mistake and damage something.

So, i was wondering... Can I put a new (blank) SSD disk, install BigSur on it, and if anything goes wrong, put the old disk back and continue using the iMac without doing anythen else? Or installing a new disk/OS will render the older disk not usable to boot my previous installation? Don' know if I explained it well.

Thanks to anyone who can help me with info or tips of some sort.

How can the older disk be impacted by the new OS, when it has already been removed and disconnected from the iMac?

 

[CooperBox]

How can the older disk be impacted by the new OS, when it has already been removed and disconnected from the iMac?

Don't overlook that the OP is a newbie to Macs in general. Many of us know that the older High Sierra SSD will be uninpacted but I readily understood the OP's query as he probably thought that upgrading his iMac to Big Sur using OCLP may interfere with the firmware resulting in the old High Sierra SSD being incompatible.

 

[FreakinEurekan]

How can the older disk be impacted by the new OS, when it has already been removed and disconnected from the iMac?

Removal & disconnection alone - even without changing versions - is not without risk. A lot can be damaged taking apart an iMac, particularly without experience.

 

[Nguyen Duc Hieu]

Removal & disconnection alone - even without changing versions - is not without risk. A lot can be damaged taking apart an iMac, particularly without experience.

What you are pointing out, is the old hard disk and other hardware are possibly damaged by THE USER.
I can't think of how a NEW MAC OS on a NEW SSD can impact an HDD that was detached from the system.

 

[dantown]

Don't overlook that the OP is a newbie to Macs in general. Many of us know that the older High Sierra SSD will be uninpacted but I readily understood the OP's query as he probably thought that upgrading his iMac to Big Sur using OCLP may interfere with the firmware resulting in the old High Sierra SSD being incompatible.

I'm glad you understood my concern, as I said, I'm new into iMacs and I thought that using OCLP could change something in the firmware and render the old disk unable to boot 👍

 

[Nguyen Duc Hieu]

I'm glad you understood my concern, as I said, I'm new into iMacs and I thought that using OCLP could change something in the firmware and render the old disk unable to boot 👍

Have you ever read the first page of OCLP?

Zero firmware patching
Using the capabilities of the OpenCore boot manager, our protocol upgrades are done in memory and are never permanent.

OpenCore Legacy Patcher

Experience macOS just like before

dortania.github.io

 

[gilby101]

I can't think of how a NEW MAC OS on a NEW SSD can impact an HDD that was detached from the system.

It is possible that a new macOS will do a firmware upgrade which is incompatible with booting the older macOS on the older disk. I don't think that is true with Big Sur going back to High Sierra, but the risk is there.

I'm really new into iMacs or Apple devices. ... and I'm tempted on updating upto Big Sur using OCLP.

With those two statements, I suggest you resist the temptation. With OCLP you are expected to have enough knowledge and experience to sort out any issues that arise (now or with further upgrades). Without some understanding of macOS booting, OCLP seems to be just magic which is great when it works, but not when it doesn't.

I started to notice that most common apps are not working anymore under High Sierra

You might prefer to sort out replacements for those causing trouble. In particular there is Firefox v115 for HS which understands new web functionality which is more recent than HS's Safari - it is also more secure.