Johnny Billquist <bqt at softjar.se> wrote: sure, there is self modifying code. The maindec zkdjb2 for example has a sequence like mov #000240,(pc) jmp (r1) and tests that the 'nop' was executed and not the 'jmp'. However, the cache, even separate i-d, is only one aspect, main point is to get all the different 'write-after-read' hazards in the pipeline under control. That's why I stayed with a simple 'prefetch-only' 11/70-like implementation in the first round. Even in that case one has to be careful and suppress for example the prefetch when the destination is pc. Otherwise a 'clr pc',often found at the end of primary bootstraps, will not do a 'jmp @#000000' but execute the opcode after the 'clr pc'. Walter