MP 1,1-5,1 Easily toggling between 10.12 Sierra and 12 Monterey OCLP?

[fhturner]

Hello—

Been a minute since I was here. Hope everybody is doin' well!

This is probably already mentioned in one of the long threads concerning running later OSes on our cMPs, but I'm not sure how best to find it. Can someone answer or direct me to a post discussing the best way to toggle between Sierra and Monterey (or later) when using OCLP and an RX 580? Monterey is running fine, but when I try to restart, I either get nothing (possibly stuck on macOS boot picker not visible due to RX 580?) or the OCLP boot picker. However, choosing 10.12–10.14 from this just results in the "NO" symbol. I'd like to be able to run FCP7, hence the need for 10.12 or 10.13 (was gonna try Retroactive). Little help?

Thx,
Fred

 

[tsialex]

OCLP does not work with anything below BigSur.

If you need to boot anything earlier than BigSur, remember that RX 580 is supported since 10.12.6, use Apple native BootPicker (see EnableGop thread) to bypass OCLP completely.

 

[fhturner]

OCLP does not work with anything below BigSur.

If you need to boot anything earlier than BigSur, remember that RX 580 is supported since 10.12.6, use Apple native BootPicker (see EnableGop thread) to bypass OCLP completely.

Hey, Alex, thanks! Right, that's why I'm getting a "No" symbol when trying something else (10.14 and under). But why wouldn't Startup Disk selection be honored and work...because that doesn't circumvent OCLP? I'll check out EnableGop. Are there any other ways to skip OCLP, aside from manually removing it from the EFI partition?

 

[tsialex]

Hey, Alex, thanks! Right, that's why I'm getting a "No" symbol when trying something else. But why wouldn't Startup Disk selection be honored and work...because that doesn't circumvent OCLP?

Nope, OCLP still loads since there are entries inside the NVRAM that instruct it to load always, except when you bypass it via the native BootPicker.

I'll check out EnableGop. Are there any other ways to skip OCLP, aside from manually removing it from the EFI partition?

There are, but are complex and involves hardware, like using the RTC NVRAM bypass and even more complex solutions like BootROM switchers - forget it.

Use the Apple native BootPicker, works fine.

 

[fhturner]

Thanks, I checked out that thread and some related resources (Lance/Mac Sound Solution YT video) and was able to get EnableGop working. Cool! I booted into High Sierra and was able to do what I needed. One issue I'm dealing with now, though, is that it appears to have done something to the volume groups on the SSD. Now each of the Monterey volumes are only showing the "- Data" suffixed portions, and the system portion of it appears to be only the volume named "Update". Troubleshooting now, but if anybody has a quick fix, I'm all ears.

Thx,
FT

 

[h9826790]

For your info, OCLP default to spoof the cMP's Board ID to Mac-27AD2F918AE68F61. This action is essential to activate HEVC hardware encoding for AMD GPU.

However, this spoofing also makes macOS believe that it is booting a Mac Pro 7,1. Therefore, anything before 10.15.2 is not supported (Board ID Mac-27AD2F918AE68F61 is not included in the macOS's white list).

If you really want to dual boot through OC boot picker, you may manually mod the OC config a bit, and use Board ID Mac-7BA5B2D9E42DDD94. This is the iMac Pro Board ID. Not ideal for cMP because some graphic card's output may be disabled due to specific framebuffer used by the iMac Pro. However, this Board ID will allow you to boot any macOS from 10.13.2 onward. Which means, you can boot High Sierra 10.13.6 to run FCP7.

However, if you aim is still to dual boot Sierra, and Monterey, then flash the cMP with EnableGop, and hold Option key to boot is the easiest way indeed. (Or, you may utilise some other boot loader like RefindPlus).