How can I port it to a new cpu?

The easiest way to run co-routines is in the idle task.  If the scheduler is running then a full port is required to swap the idle task in and out.  However, if you know that only co-routines are ever going to be created and never any other tasks then you could ignore the context saving and restoring and just write a normal interrupt for the tick.  This should in theory make for a very simple port and system but I have never tried it ;-) Regards.

Thank you Richard.