I have a 4TB installed. After having formatted to GPT exFAT through Windows disc management , the Prime4 would give me an error stating that it was incompatible and to format to FAT32 or exFAT. After clearing the message, the drive still worked in the prime 4. Played for hours without any issues.
However, the error message was getting to me. So I decided to try some utilities to see if there was some workarounds. What I did was convert MBR to GPT through Windows disc management. Then I used the latest version of DiskGenius to format the drive in exFAT using all format defaults. I now get no error messages on the Prime4 and no problems during playback so far. And yes I can use a 4TB drive as I have very large FLAC files and have a huge collection from the 50’s to current.