Few days ago a hack had been released which allowed NES Classic Mini owners the ability to edit and add to the 30 games which come pre-loaded on the console out of the box.
A new hack has now emerged which goes one better; you can now put the full NES library onto the machine.
The process requires a PC and, as you can see from the video guide, is quite time consuming. It also goes without saying that deploying such a hack has its risks, and should the process go wrong, it’s unlikely that Nintendo will be too sympathetic should you try and arrange a repair under warranty. Finally, there’s the obvious caveat that using ROMs is legally questionable.