So far (2021, Sept 19) Big Sur 11.6 generally works well (Mac Pro 4,1 flashed to 5,1).
11.5.2 to 11.6 took about 45 minutes including multiple (natural) auto-restarts.
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I only (rarely) get hanging-reboots when I'm experimenting with configurations.
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My worst issue is; My bluetooth driver doesn't always load when booting up.
I upgraded to Bluetooth 4.0 (including a wi-fi upgrade).
I could have installed Bluetooth 4.2, but I want to (also) be compatible with Mavericks 10.9.5.
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Occasionally my USB wired mouse won't "initialize" when booting up.
But my bluetooth mouse may (instead work).
A restart almost always fixes one or both issues.
My USB wired mouse must be plugged in before I boot up.
My wired USB keyboard & USB flash-drives always work (as usual).
So, this is not a general" USB issue (maybe a mouse related issue).
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Big Sur doesn't know what Firewire is (Big Sur partly freezes).
I boot into Mavericks to use my old Firewire peripherals.
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This post is a record of my notes (processes); incase it helps.
I'm a novice, so I'm not advising. My testing is ongoing.
Please research anything I state, before you apply.
Some of my terminology may not be accurate.
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Here's my computer's (current) IMPORTANT upgrades.
Mac Pro 2009 > 4,1 flashed to 5,1.
Cleaned BootROM including a number of IMPORTANT fixed issues.
Mac Pro firmware version 144.0.0.0.0 (before Big Sur upgrade).
2 x 3.46GHz 6-Core Intel Xeon Westmere processors (replaced old Nehalem versions).
64GB 1333MHz RAM.
SSDs (SATA solid-state hard-drives) + sleds.
Radeon RX580 8GB (Metal support).
Bluetooth 4.0, AirPort Extreme (0x14E4, 0x111) > adaptor kit.
Mac Magic Mouse 2 (Bluetooth). A generic wired USB mouse (for backup).
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Big Sur installation process (after the above upgrades):
OpenCore-Legacy-Patcher (see the links section below).
Version 0.2.4 (includes Latebloom boot "race" fix < an IMPORTANT improvement).
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Caveat notes:
A cleaned BootROM was IMPORTANT for me (thank-you
@tsialex).
See the links section below.
After installing the new (clean) BootROM, I re-ran OpenCore-Legacy-Patcher 0.2.4.
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Once I installed my 3.46GHz 6-Core Intel Xeon Westmere processors,
my RAM showed 1333MHz , instead of its original 1066MHz.
Meaning: My old Nehalem processors only allowed a max of 1066MHz "RAM speed".
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I had a "fatal" garbled audio issue until I upgraded my
old Nehalem processors to Westmere (thank-you
@tsialex).
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My (SATA) 6Gb/s solid-state hard-drives max out at 3Gb/s (normal for my machine).
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I have a 250GB SSD (SATA) for booting into Mavericks or Mojave.
Above: Can be used if Mac Pro 5,1 is having a Big Sur boot-up issue.
Mavericks/Mojave (when used) > SATA bay 1. Big Sur SATA bay 2 (permanent).
Mavericks must be in "bay one" when I perform (occasional) BootROM cleaning.
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Mavericks doesn't fully support my Radeon RX580 GPU. Works good enough for me.
I also run a different (virtual) installation of Mavericks inside Big Sur (via Parallels).
There, my Radeon RX580 GPU (with Mavericks) is "fully" supported.
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BootROM repair services by
@tsialex:
Please fully read this first post, you will probably find that you have one or more problems described into the various notes below. Mojave will only install if you have upgraded your BootROM to the current release and your Mac Pro have a Metal capable GPU*. If you are trying to install Mojave...
forums.macrumors.com
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OpenCore-Legacy-Patcher (install Big Sur on an unsupported Mac):
Experience macOS just like before
dortania.github.io
Experience macOS just like before. Contribute to dortania/OpenCore-Legacy-Patcher development by creating an account on GitHub.
github.com
YouTube instructional video:
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