Even though the form factor is (nearly) identical there are two different 'PCMCIA' card types around:
real (=old) PCMCIA: 16 bit ISA style = compatible w/ A1200/600
CardBus: 32 bit PCI style = not compatible
Usually you're not even be able to insert a CardBus card into a PCMCIA slot all the way (to protect the 3.3V card from the 5V in the slot).
