Are you refering to the online saccade detection by the eyelink (operator PC) itself, or did you program this code yourself?
I am not aware of begin_realtime_mode & end_realtime_mode functions. I presume these are part of the new API’s. If so, they’re not part of the eyelinktoolbox (for that reason). In the eyelinktoolbox code there are two examples (eyelinkexample.m & eyelinkeventexample.m) of how to create reasonably fast gaze contingent experiments. But, c will always out perform matlab code. So, if you need to do a lot in real-time, and can’t prepare your stimuli, I would suggest to use c. You can of course also use a hybrid approach, and only c-code the time critical part of your experiment, and create a mex file for that. I don’t believe you can compile PsychToolbox and eyelink toolbox code as such (I have never tried). There’s also a few ways in which you can improve performance of the eyelink, e.g. do not use filtering, shaves 4 ms of the response time (but gives less accurate saccade estimates).
