Why did PowerMac G3 and G4s have 64-bit PCI slots?

Question

Do a Google Image search on the motherboards of the original PowerMac G3 and G4 systems, and you'll notice several 64-bit PCI slots.Coming from a PC enthusiast background, 32-bit PCI seemed perfectly serviceable, with 64-bit only ever seen in exotic server configurations.What benefit did Apple see in adopting 64-bit PCI in these systems, what kinds of cards actually took advantage of this technology, and why was it never a thing in mainstream PC computing?

Andys · Accepted Answer

32 bit PCI was only capable of 133 MB/s, but at the time, high speed SCSI peripherals were popular, and 64 bit SCSI cards were capable of 160 MB/s.If I recall correctly, the PCI bus was shared and not point to point like PCIe, so if you had multiple cards it made sense to buy high end 64 bit cards for that reason.

devl547 · Answer

Simply speaking - more bandwidth due to increased bus width. And later increased frequency in PCI-X slot.But lack of useful desktop/workstation hardware and adoption of PCIe on PCs killed it.