The canonical "bug that hides from breakpoints" was used for copy protection in some early pc games it involved writing code into the instruction stream but not

The canonical "bug that hides from breakpoints" was used for copy protection in some early pc games it involved writing code into the instruction stream but not executing it because that location was already in the prefetch buffer. Try an single step through there or set a breakpoint and the debugger would see the written code not the original