My wife's cMP 3,1 with updated WiFi/BLE has been running 10.13.5 on a Fusion drive with HFS+.
It has 16GB of RAM and an Apple Radeon 4870. A spike knocked out part of the RAM (waiting for replacement, now on 8GB) and the card. I replaced it with an Apple Radeon 5770. But the graphics system was in safety mode with serious tiling.
I reinstalled with the dosdude patch, same result.
After getting a used 4870 from eBay and putting that back in all is well. Clearly, the patch and drivers somehow do not support the new drivers running with the 5770 and maybe other cards.
El Cap worked fine with the 5770.
It has 16GB of RAM and an Apple Radeon 4870. A spike knocked out part of the RAM (waiting for replacement, now on 8GB) and the card. I replaced it with an Apple Radeon 5770. But the graphics system was in safety mode with serious tiling.
I reinstalled with the dosdude patch, same result.
After getting a used 4870 from eBay and putting that back in all is well. Clearly, the patch and drivers somehow do not support the new drivers running with the 5770 and maybe other cards.
El Cap worked fine with the 5770.