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Disk Utility should be able to wipe out any existing partitions before attempting to install a new OS, but my favorite fallback is to use a Windoze PC to 'clean' drives to get back to basics before a new install. If you have access to (almost any PC with a USB port) and you have a USB to SATA cable to plug-in a bare drive externally, then I start by right-clicking the start menu to get to the legacy start menu and then select Disk Management. Disk Management is like Mac's Disk Utility, but I use it first to get an overview of the drive(s) before starting. The takeaway there is usually visible to the left where it shows you the disk number assignment(s) by the OS. The boot volume will usually be Disk 1 and the external (or other) drives will be 2, 3, etc.

While keeping Disk Management open, go to the taskbar and type: cmd to launch a terminal window (aka DOS command interpreter). At the prompt type: diskpart - which will usually open a new window with a different prompt. At that prompt type: select disk 2 (assuming your recycled drive shows as that number in Disk Management). Make certain that you have selected the correct drive (measure twice/cut once) and when confident type: clean and press return. At this point you can close the command prompt windows and the Disk Management window will now show the drive you just wiped as uninitialized. At that point you've blanked out the drive and back on the Mac you should see this reflected in Disk Utility. If you use Disk Utility to initialize the drive it would be advisable to start by formatting it as a GPT (GUID Partition Table) first (MBR is now the best option for bootable flash drives) and then creating Mac partitions as needed. You will probably want to use APFS for SSDs but Mac HFS works fine for spinning media.

My cMP 3,1 has a 1.92TB Samsung SSD that I have multiple partitions on. The primary (450GB) partition is now Sequoia, and I also have legacy Mac HFS partitions for High Sierra and Mavericks with the remaining space formatted as a Mac HFS data volume. This configuration is not without some problems. I upgraded the original GPU to an inexpensive used metal-compatible RX570 which OCLP provides the means of loading kext drivers so once the EFI partition is loaded at startup provides a boot picker that now allows all three OSes to display and load. I had originally used dosdude1s patcher to get High Sierra to load and ran it again on the Mavericks partition to get his kexts to let me almost use Mavericks. I say almost works because the RX570 is not actually recognised correctly by the OS and without the original GPU acceleration and VRAM some legacy apps (like Apple Compressor) do not work yet and I have little hope that there will be a solution other than swapping out the GPU with the original card if I need to go back.
 
I put a brand new ssd into the MacPro 3.1 and installed El Capitan from my boot thumb drive. This worked well and El Capitan is back running on my computer. Unfortunately, I now find that two of the 3 drives (that were working well before I started all this) are no longer accessible. They do not appear on the desk top or anywhere else I can see, except that they are indeed listed in Disk Utility. Disk Utility says that they are both full, although they are really not full. I'd really like to access these drives but I don't know how to do it. Suggestions will be greatly appreciated.
 
The two disks that I can no longer get access to are the two that I tried to install Monterey with the OpenCore Legacy Patcher. I've run disk utility repair on both but it did not help. Again, I can see the disks in Disk utility, but I cannot see the disks from the rest of the mac. Bummer. I want the files on those disks.
 
I want the files on those disks.
Chances are slim, but there are a number of paths to a resolution of your issue either way.
First off, did you leave the Time Machine disk untouched or at least, can you still see your previous instance states from before the upgrade attempt in Time Machine?
 
Chances are slim, but there are a number of paths to a resolution of your issue either way.
First off, did you leave the Time Machine disk untouched or at least, can you still see your previous instance states from before the upgrade attempt in Time Machine?
Yes, indeed. The back up disk looks fine. I have not tried to open time machine but I'm hopeful that it will be able to bring back my files. The two disks that I cannot see were both used as targets to install Monterey with Open Core Legacy Patcher. THat is probably what did them in. I've not used time machine ever before but will study up on it before I try to use it. Thanks for the idea.
 
I've not used time machine ever before but will study up on it before I try to use it.
You basically need to boot into recovery and select the option to restore from Time Machine there. That is, not from Mac OS itself. Starting up a Mac OS USB install disk should bring the recovery options up. Since you have recently reinstalled El Capitan, you might still have the install disk you created. If so, start this up to get the restore option.

Use Disk Utility to prepare a volume to recover to beforehand. Disk Utility will also be available when booted into Recovery. You might want to ensure your new reinstalled El Capitan instance has a different name to the original one.

If you can't get into Recovery because your GPU cannot show the screen, there are ways around this. I think it should show up in most cases but a bit hazy on that part now. I actually got into using alternative tools for booting mainly because I was concerned about recovery access to Time Machine when I first updated my GPU to one without native boot screen.

I think it turned out to not be an issue but I forget now. In any case, there are tools that will ensure the screen is shown on almost every GPU and I had started using one of such. I my case also, I actually decided Time Machine was not the best option for me and i started using Carbon Copy Cloner, which allowed access from Mac OS.

I digress though. Main thing going forward is to always ensure you never overwrite your working setup or that you back such up before overwriting.

After you hopefully get El Capitan restored, can look again into getting the newer unsupported versions in place.
 
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You basically need to boot into recovery and select the option to restore from Time Machine there. That is, not from Mac OS itself. Starting up a Mac OS USB install disk should bring the recovery options up. Since you have recently reinstalled El Capitan, you might still have the install disk you created. If so, start this up to get the restore option.

Use Disk Utility to prepare a volume to recover to beforehand. Disk Utility will also be available when booted into Recovery. You might want to ensure your new reinstalled El Capitan instance has a different name to the original one.

If you can't get into Recovery because your GPU cannot show the screen, there are ways around this. I think it should show up in most cases but a bit hazy on that part now. I actually got into using alternative tools for booting mainly because I was concerned about recovery access to Time Machine when I first updated my GPU to one without native boot screen.

I think it turned out to not be an issue but I forget now. In any case, there are tools that will ensure the screen is shown on almost every GPU and I had started using one of such. I my case also, I actually decided Time Machine was not the best option for me and i started using Carbon Copy Cloner, which allowed access from Mac OS.

I digress though. Main thing going forward is to always ensure you never overwrite your working setup or that you back such up before overwriting.

After you hopefully get El Capitan restored, can look again into getting the newer unsupported versions in place.
Thank you so much, Dayo, for your advice. It worked out great ! I first put a new clean drive into the MacPro that was as big as the backup disk, then installed ElCapitan, then did the Time Machine from the Recovery Page. I've got many years of pictures and files back. Awesome. Thank you very, very much !!!
 
It worked out ... got years of pictures and files back.
You had the basic requirement of a backup system in place.

Moving on to newer versions of Mac OS is not a major item these days.
The main decision to make is on which of the possible methods you want to use.

To go beyond Monterey, OpenCore, with OCLP patches, is needed.
To go beyond Catalina up to Monterey, OpenCore needed. Some GPUs require OCLP.
To go beyond El Capitan up to Catalina, DosDude patched instances are probably best.

I would start with installing DosDude Catalina.
Gives a pseudo natively supported APFS instance.
Allows bridging between APFS/Non-APFS instances later.

As mentioned before, never overwrite your working instance.
 
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I have recently upgraded my MacPro 3.1 from macOS Mojave to macOS Monterey,
after some time it finally installed and boots up well.
I did notice before upgrading that installing Monterey on a MP 3.1 would reduce the CPU usage
to only 4 cores, which has certainly happened in my case.
What I did not expect was the the other OS's on my Mac would be affected too.
I have El Capitan, Sierra and another Mojave install on this mac
and all now are only running on 4 cores, which is noticeable in the machines reduced performance.

Is there anyway to get back to 8 core function on at least the older OS's on this old slugger.


Thanks
 
Yes, you can revert your 3,1 to 8 core operations by running OCLP again and this time select Settings from the main window and then uncheck the MacPro3,1/Xserve2,1 Workaround option that was enabled by default when you opted to install OCLP and Monterey on your 3,1. Once that has been checked and the build has been reinstalled your MacPro will be set to use dual CPUs again with the caveat that you may have some issues with the later OS(s). Perhaps the single CPU issue is something the OCLP dev team still has in mind and will eventually also be patched(?)
 
Hi

Thank you for responding.

As suggested I rebuilt Open Core with the MacPro 3.1/ Xserve 2.1 unchecked.
After rebooting I was back to running 8 cores on macOs Mojave.
I was also able to boot to macOS Monterey and it too was running on 8 cores.
Great! I thought that is that issue solved.

But sadly no, on booting back to Mojave that was fine, but booting back to Monterey a second time
would only result in the Mac booting back to Mojave,
From the boot picker I can select the OC EFI, the mac then just reboots into Mojave, it does not as it
should go to the next boot picker screen where I can select Monterey.

As a test I decided to re build OC with the MacPro workaround selected.
The mac will now boot to Monterey which is good, but of course only 4 cores.

I will try rebuilding with the workaround unchecked and see if the issue is replicated,
just in case it was something else causing the problem.

A few other things is the mac will not go to Sleep, the display goes off but the mac stays fully powered up.
Is there anything I can do about that?

I new that installing Monterey via OC would disable Bluetooth I just didn't realise that it would affect other OS installations that are on this mac, El Capitan, Sierra and Mojave.

And I don't quite understand why AirPlay is not working on Monterey, whereas on Mojave it works.
In the Music app if I select the AirPlay icon it shows my AV Receiver and my TV and both are selectable.
But if I press Play the sound only comes out the internal speaker instead of automatically switching to the selected device, after a number of seconds I get a notice saying it cannot find the selected device and to check network settings and or AirPlay settings. In Mojave I don't have to do anything it just plays
 
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Running the latest version of Open Core 2.4.0.
No, what you mean is that you have used v2.4.0 of the OCLP, a tool for setting OpenCore up, to configure OpenCore, a tool for booting stuff, of which the latest version is v1.0.4. That is, the latest OCLP is v2.4.0 and the latest OpenCore is v1.0.4. After using the OCLP to set OpenCore up, you end up running OpenCore (to boot stuff) and not the OCLP (does not boot stuff).

At this time, the OCLP probably does indeed set you up with OpenCore v1.0.4, the latest version, but note that not every OCLP version does this but set things up for older OpenCore versions from whatever is current ... not really an issue.

It is not neccesarily a good idea to use a current OCLP version to set OpenCore up for an older version of Mac OS as OCLP development effort is always focused on getting the current latest Mac OS, Sequoia at this time, to work with OpenCore by patching the Mac OS installation etc. If you want to to use the OCLP to set OpenCore up for Monterey, you might want to consider an older OCLP version that was focused on Monterey instead.

Note though that the MP31 does not need OCLP-configured OpenCore or OCLP-specific patches to run Monterey if using a GPU that is supported on Monterey. With such supported GPUs in place, the OCLP should only be used to configure OpenCore for Ventura/Newer and should only be used for Monterey/BigSur if running a GPU that is not supported by those versions.

Also bear in mind that OpenCore is not easily set up to run several generations of Mac OS as you have and that the OCLP definitely does not do this. Additionally, OCLP-configured OpenCore is set up to take over your boot setup. So you have a situation where every time you start your MP31 up, an OpenCore instance basically targeted at Sequoia is loaded.

This is where MyBootMgr can help (See Link in My Sig). One minute, I am in 15.x Sequoia, which demands using 4 cores on MP31, via one OpenCore instance and next, with all 8 cores, in 11.x BigSur via another instance or 10.7 Mountain Lion or even 10.4 Tiger via yet another. Each OpenCore instance is configured for specific Mac OS generations. I forgot to mention that along with the 16 Mac OS versions that I boot via OpenCore, I also run DosDude Catalina, Windows and Linux without OpenCore on my MP31 ... all without issue.

Before changing your setup though, try adding "-no_compat_check" to bootargs in the OpenCore config file, setting the "WriteFlash" config key to "false" and then resetting your nvRAM. If that doesn't help, you might want to look at MyBootMgr. Good luck!
 
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