Just wanted to let you know what I have been able to build, might want to update as well.

I have 10.15.6 Catalina running on my Mac Pro 4,1 flashed to 5,1 (simple firmware flash update you can do)

12 core 3.66 W with 64 GB Ram 1333mhz

RX 5700 xt GPU

Booting from NVMe SSD via PCIe expansion tray

USB type c and USB 3.0 via PCIe expansion card

First, you have to be willing to get your hands a little dirty. In order to get a GPU like the 5700 running, you have to do a PIXLAS mod...this involves taking the Power core out of the machine, purchasing a cable to then splice the wires coming out of the power core...this is so you will bypass the thin wiring on the motherboard to the Mini 6 pin power ports....you go straight from the power core to the GPU which is 6 Pin and a 8 pin....if you just YouTube PIXLAS you will see a great video on how to do it and where to order tools and wire needed.

But to get that 5700 card to work on the machine, you have to be running 10.15....

You need to turn off SIP on you 5,1 running Mojave, while in recovery mode, open terminal:

csrutil disable

Restart computer to take effect.

Then you need to open terminal and enter this command, can be in normal boot up mode, not recovery mode.

sudo nvram boot-args="-no_compat_check"

Now, you have to get your hands on a compatible computer that is running Catalina 10.15 already....get an SSD or HDD and hook it up to the computer via external drive. Boot into recovery mode, format drive to apfs, via disk utility, and then install Catalina 10.15 on that external drive....then take that drive and stick into the Mac Pro 5,1.

Your Mac will now be running Catalina 10.15. (I was running Catalina even with my old RX580 GPU), you can now use time machine to rebuild your system in 10.15.

You can now take out your GPU and slap in the rx 5700 xt, plug in the cables coming from the PIXLAS mod and you will be good to go!

I also used Carbon Clone Copy to clone my SSD on to the MNVe drive and that is how I am booting from NVMe drive (note: you have to have BootROM 140.0.0.0.0 version, without this version your 5,1 will not recognize NVMe drives…mine got updated via Mojave install)

Now the great simple task of getting Boot screen and native OS updates through Mac app store (since officially 5,1 is not supported passed 10.14) you need to download OPENCORE. Here is a video that shows you the simple process to do that. Package download in video description.

Note: when I mounted my EFI, it did not have an EFI folder in it, so I just dragged the whole EFI folder from the download.

Aslo, you can re-enable SIP as well, VIA terminal while in RECOVERY mode.

csrutil disable

csrutil enable

Also if you are interested in this mod but think its to complicated, its not....some may just stay with the RX 580 bc its plug and play but check out these bench scores when compared to the RX 5700 XT in a 5,1 Mac Pro set up. The RX 5700 XT blows it out of the water.

https://barefeats.com/cmp-5700-xt-vs-other-gpus.html

NOTE:

I did have to go with the PowerColor Red Dragon version of the RX5700 XT.

https://www.amazon.com/gp/product/B07WNYZJ7Y/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

All other builds were to tall in the 5,1 and covered up the extra 4x PCIe slot needed for the USB card in my machine…from what my research could conclude, the main difference from PowerColor or Gigabyte, Saphire, etc. is the cooling design for the GPU. But I have my rig in an open area under my desk with proper ventilation and have not seen any issues with throttling due to excessive heat.

Questions about this, feel free to email:

BenR.Edit@icloud.com