MP 1,1-5,1 Mac Pro 2010 - is flashed RX 580 preventing OCLP Monterey install?

[sirroderick]

Can't seem to install OCLP Monterey on my 2010 Mac Pro. I've successfully installed it on my other two 2009 Mac Pros and I'm just applying the same procedure with the 2010 model but the installer USB gets stuck right at the 'reboot with OPT key pressed' stage. Basically the installer won't mount. I've tried multiple times recreating the installer with different drives but to no avail. Apart from being a 2010 model the only other difference is it has an RX 580 8GB video card installed. The card works perfectly with High Sierra and also an old OCLP install of Catalina from a couple of years ago so is definitely not faulty per se. It does have a flashed Mac boot screen though. Could this be the source of the problem?

 

[Dayo]

Could this be the source of the problem?

It could be. Some cards flashed by MacVidCards are known to fiddle with things in the early boot stage. There is no issue with this if going on to boot Mac OS directly but it can lead to problems with using third party loaders.

The MyBootMgr guide has this to say:

You can try running the process with another card to exclude this as a factor.

 

[sirroderick]

Thanks Dayo. You're right I should try another GPU first to confirm. It is odd that the RX 580 works fine with an older version of OCLP and Catalina though. If it does turn out to be the flashing can it be fixed? or do I have to dump the card?

 

[Dayo]

Thinking about it, if it is because of the MVC/APFS issue, you should be able to get things working by the "EnableJumpstart" key to "true" in OpenCore.

This is equivalent to the "SupplyAPFS" feature that overcomes this problem in RefindPlus.

 

[sirroderick]

Well this is weird. I got so fed with messing around with this machine that I put it in a corner and forgot about it for a few days. I'd created endless OCLP installers on various drives but none would mount. Lo and behold I pulled it out this morning (with an OCLP installer USB stick still plugged in) and powered up. Lo and behold the installer mounted and worked without a hitch. It did get stuck at the location manager necessitating a force quit but it then booted into Monterey without a hitch and seems to be working great, RX 580 and all. OCLP sure works in mysterious ways. Bordering on voodoo.😀