as Sasha describes above, with CMOS it is not the DC load (typ 1 uA or so) but the capacitance that matters. Thus the question is not "how many loads can it handle" but "how fast can I run with the loads I have". The "traditional" '51 port is not a very efficient design for driveing capacitive loads.

For that very reason, many modern '51 derivatives have configurable ports and when such ports are configured as push-pull you can attain acceptable speeds even with several CMOS loads.

the moral: If you need high speed, use a derivative with configurable port pins or use a buffer such as '240-'245.

Erik

NOTE: Using "traditional" derivatives with one or 2 chips connected to a pin and 11.0592 MHz clock, there is not a problem if you keep your interconnect short. However, if you go much up in speed you must use a push-pull configured pin, if you drive an interconnect the buffer is mandatory.