Thanks PaulS. If Arduino cannot send bits(?) bytes(?) serially at right moments in time at high baudrates, then this feature limits any serial communication, including serial microSD cards, other Arduinos etc ? If so, I have a bigger problem than expected. USB 2.0 (USB - Wikipedia) can transfer
480 megabits per second (57 megabytes/s) , but Arduino cannot utilize that (?), only about 10 kilobytes/s. Sigh.
Other cheap, quick and dirty methods to consider for high speed data transfer to host?