If this option is on, IDA will simplify instructions and replace them by clearer pseudo-instructions. For example, or 0, 0, 0 will be replaced by nop If checked, IDA will use mnemonic names of the registers: %r26: %arg0 %r25: %arg1 %r24: %arg2 %r23: %arg3 %r28: %ret0 If this option is on, IDA will disassemble instructions as if PSW W bit is on, i.e. addresses are treated as 64bit. In fact, IDA still will truncate them to 32 bit, but this option changes disassembly of load/store instructions.