I wanted to thank everyone , especially the OP, for giving me the info and confidence to upgrade my 5,1 GPU.
I followed the info upgrading firmware incrementally to 138.0.0.0.0 then finishing the full Mojave install thinking it would go on to 140.0.0.0.0 which it did not.
Everything worked with my rx580 pulse and since I didn’t need nvme support I didn’t worry about it.
To get a little more performance I decided to get a Samsung 860pro ssd on a OWC pcie adapter.
I tried doing a new install on the new drive but the installer said the drive was too small even though it was twice the size of the original startup drive.
Just for fun while the installer was running I opted to try to install on the original startup drive and much to my surprise it did the firmware update to 140.0.0.0 and even more surprising I had a BOOT screen showing the progress of the update with only the pulse rx580 installed.
Once the update was done, I used carbon copy cloner to clone the startup disk to the new Pcie ssd, selected it in the startup menu, and booted up.
The black screen returned using the cloned drive , but everything worked as it should.
I just thought it was an interesting quirk that I wanted to share.
Thank you all again for taking the time to post.
I followed the info upgrading firmware incrementally to 138.0.0.0.0 then finishing the full Mojave install thinking it would go on to 140.0.0.0.0 which it did not.
Everything worked with my rx580 pulse and since I didn’t need nvme support I didn’t worry about it.
To get a little more performance I decided to get a Samsung 860pro ssd on a OWC pcie adapter.
I tried doing a new install on the new drive but the installer said the drive was too small even though it was twice the size of the original startup drive.
Just for fun while the installer was running I opted to try to install on the original startup drive and much to my surprise it did the firmware update to 140.0.0.0 and even more surprising I had a BOOT screen showing the progress of the update with only the pulse rx580 installed.
Once the update was done, I used carbon copy cloner to clone the startup disk to the new Pcie ssd, selected it in the startup menu, and booted up.
The black screen returned using the cloned drive , but everything worked as it should.
I just thought it was an interesting quirk that I wanted to share.
Thank you all again for taking the time to post.