Serial com between arduino mega 2560 and atmega 328p(arduimu v3)

AWOL:
yesthereisyoucan'treadthiseasilybecauseIhavenotputinthecuesthattellyouwherewordsbeginandend.
But if you slip in some simple whitespace and punctuation, things are a lot easier.
Computers don't read junk either.

You need to be sure not to send data faster than the receiver can handle that. The point of sending "abcd" over and over as fast as possible escapes me.

You seem to have been trying to detect whether there was a problem with doing that, and you seem to have proven that there is.

Now, what do you intend to do to fix the problem? Or, is the problem that you don't know how to fix the problem?

guys, really thanks a lot!
I will slip in the "junk" & try lower down the baud rate.