CardBus Compatibility
Like the PowerBook 5300 series, the 3400s came with a pair of PC card slots, but whereas those on the 5300s were strictly 16-bit device compatible, those on the 3400s were, in theory at least, compatible with 32-bit CardBus cards being based around the 32-bit Texas Instruments PCI1130 PC card controller. In reality, the PC card slots were designed to physically accept only 16-bit cards, though many users have managed to get a variety of CardBus cards to work with them. Using CardBus cards allows 3400 Series PowerBooks to be used with, for example, USB devices like printers and FireWire devices such as iPods.
Read more about this topic: Power Book 3400c