Quote Originally Posted by Jonathan View Post
The opto-isolators are very unlikely to be the limiting factor on a breakout-board as most parallel ports struggle stably to output more than around 35kHz.
Actually you'd be surprised how many problems come from slow opto's and I've seen plenty of people on the Yahoo forum have all sorts of troubles with cheap Boards using slow opto's.!!

Must admit Thou personally I've never had any problems.!