I have some familiarity with 68K and 6502 Assembly, and not much with Intel assembly. So, my question is this. What is the performance advantages of using Intel string instructions such as MOVS and CMPS as compared with just for instance writing a character with MOV in a simple loop?

My brief investigation into the subject via Google has shown me contradictory answers to this question.

Thank you for sharing your knowledge.

Jason

I don't know, I've always used a byte-wise comparison and mov.

I've never tried those, so I'd be interested in hearing what others have done.

You should be able to use both, and if you need more speed in a performance critical section, you can try to not use the string instructions. Intel has not bothered to made these instructions fast, although that may have changed with the newer processors.
I recently encountered a speed boost on ivy bridge by changing stosq to mov dword[rdi],eax; lea rdi,[rdi+8], but this may mean nothing for your needs.
Bottom line: try both and see which one is faster for you.

Don't guess, measure.

Empirical evidence always wins, yo!

one more thing, 68K != modern intel/amd processor. Completely different ball games.