as title says i can't use more than 2 display on my mac pro 2013 (the cilinder) os high sierra 10.13.6. i've installed windows 10 on a partition and i can use all the display available.
can you help me to fix this problem on osx partition.
thx in advance
Unfortunately all AMD Drivers are native to the version of MAC OS you have installed. You will need to open a APPLE Support ticket.
You can possibly install Windows Boot Camp OS in your MAC PC and use the latest Boot Camp AMD Driver available to see if it works the same as regular Windows OS by supporting more than 2 Displays at the same time.
There are five newer MAC OS version, Mojave, Catalina, Big Sur, Monterey, & Ventura. This MAC Website shows which MAC OS versions are compatible with your MAC Pro 2013: https://www.macworld.com/article/673697/what-version-of-macos-can-my-mac-run.html
If you upgrade your MAC OS to the latest version that is compatible with your Mac Pro it will also have the latest AMD Driver version natively embedded in the MAC OS.
Besides the newer versions of MAC OS might fix your problem of having more then 2 Displays supported by new features or drivers.