[eddie_catflap]

I remember the knowledge/idea of illegal opcodes for the C64 slowly making their way through the hacker/cracker community. Like secret knowledge being distilled back then via BBS

[toolslive]

they were quite useful. I distinctly remember there were undocumented NOPs consuming a different number of cycles than the default one EA. These were fe used to pad raster line interrupt routines with cycle precision. (damn, I'm old)

[selcuka]

IIRC the "normal" NOP took 2 cycles, so we used the illegal ones to waste an odd number of cycles for accurate raster line timing.

[croemer]

What do you mean by "fe"? "For example "?