Sorry but this sounds like jumping to conclusions, going off only the fact that you can fence off some memory in the BIOS. See eg this windows gaming site review where they couldn't find a difference in the performance between allocating 64MB or 2GB save for satisfying some games that need to detect a certain amount of GPU memory to start: https://www.techspot.com/article/1578-amd-raven-ridge-reserv...
But I don't doubt there still exist software (Firmware, OS, driver, graphics API) problems where unified memory ends up being used badly. There doesn't seem to be evidence that much if any of it are because of hw limitations.
But I don't doubt there still exist software (Firmware, OS, driver, graphics API) problems where unified memory ends up being used badly. There doesn't seem to be evidence that much if any of it are because of hw limitations.