What is the maximum processing speed of NIOS II?

There cannot be more instructions processed than are started: only 1 instruction can be completed per cycle so 6 * 185 cannot be. The max is 185 and it is not only branches that degrade, it is any dependency where an instruction depends on the results of a previous instruction. of course not as severe as branches. Another thing to watch for when looking at benchmarks is compiler optimizations of the benchmark code that make it look like more than 1 instruction executes per cycle. Cache misses that stall the pipeline have to be considered ... usually by factoring in the cache hit ratio.