when 128k is not enough

[Ioannis]

commands like hserin hserout block until they complete whereas in arduino c the equivalents serial.print() and serial.read() are both interrupt driven out of the box

You have a good point Richard. Fortunatelly DT-INTS can help on this, though needs a little work from the programmer to make a ring buffer. Not out-of-the-box, but close.

Good thread this one.

Ioannis