Terminology confusion? NMEA usually refers to an RS232 format, where the speed (baud rate) is set independently (e.g., 9600). OTOH two wire ARINC data standards usually offer ‘fast’ or ‘slow’.
^^^^^^THIS^^^^^^It is not the baud rate. In the garmin portable world, the NMEA fast or slow determines the interval of how often the NMEA data payload is sent. It also changes the specific content of what data is sent in each transmission (fast includes fewer data elements). I once resolved a connectivity issue by changing this setting.
Larry