From Appendix A.3 of the user manual:
Unless otherwise specified, the Rabbit I/O buffers are capable of sourcing and sinking
8 mA of current per pin at full AC switching speed. Full AC switching assumes a
29.4 MHz CPU clock with the clock doubler enabled and capacitive loading on address
and data lines of less than 70 pF per pin. The absolute maximum operating voltage on all I/O
is 3.6 V.