USB universal serial BUS .. which works on 4 lines (v+, v-,d+,d-) ...devices r connected to this port n it carries out operations according to host controller !!
PCI (peripheral component interconnect) is different bus architecture! many devices r connected to PCI bus n depending on priority n request to use bus by device... transaction takes place...
bus width can either 32bit or 64bit
Shiv
hmmm what the above ones said are not exactly correct.....
PCI supports hot plug support too......
all PCI devices are not parallel data transmission... (ex: PCIe uses serial - deserialization at phy layer)
the main differences between USB n PCI is the protocol.
USB control transfers data serially and the protocol is very easy!
where as in PCI, data is transferred like a normal lan traffic(layer based) i mean its in the form of packets!!!
PCI is very useful for very high speed secured traffic like graphics, audio etc..... where the turn around time n the data security is important!
where as USB r mainly useful for external devices!!
PCI has numerous advantages like power management, interrupt handling which are not there in USB!
Keep in mind though that USB supports the Suspended state and the Resume signaling - specific to the bus power. The suspend current is 500uA. Additionally, wrt device/system power management, any such power management scheme can be implemented on top of the USB protocol controlled by the system software.