as the first prevent an hypotetical 4 Mo display memory ?
The docs says that the hardware cursors are located in the upper 16k of display memory (or upper 4K of each logical memory plane).
0x1fc000 has been there for years before I picked up the GD5429 again, and I try to modify as little code as possible for each change. Also the currently emulated cards don't support 4MB anyway.