Among the things to think about when dealing with central storage in 31-bit addressing mode are the use of the load real address (LRA) instruction, the use of the LOC parameter on the GETMAIN macro, the location of the DAT-off portion of the nucleus, and using EXCPVR to perform I/O. (EXCPVR was described in the section Performing I/O in 31-Bit Addressing Mode.)