They both disable the Co Processor, but do work differently.
*FX 151,230,14 selects a special Co Processor (call the the Null Co Processor) which tricks the MOS into thinking there is nothing present.
The *FX setting is not remembered across power cycles, but you can set the default value by editing the cmdline.txt file on the SD Card.
For example, this will cause 14 to be the default on power up:
Code: Select all
copro=14 copro1_speed=3 copro3_speed=4 tube_delay=0 elk_mode=0