mdj wrote:
"Real" busses connect system components in terms of a processing units native address space, providing a more-or-less seamless interconnect void of marshalling.
Actually, I was referring more to the physical layer, where a single (multi-drop) "bus" connects devices electrically and the transmissions of each device are seen by everything attached to the bus. Of necessity, there's an arbitration mechanism and strictly only one device can transmit at any one time.
USB, OTOH, is actually point-to-point, and different 'bus' segments are bridged and switched via hubs. That's why you have a USB 'host controller' for every USB port in your PC, and why you've never seen USB devices 'daisy-chained'.
It may also interest some of you to know that PCI Express (PCIe) is also a point-to-point protocol, using multiple 'root complexes' and switches making it more like USB than PCI.
Regards, -- | Mark McDougall | "Electrical Engineers do it | <http://members.iinet.net.au/~msmcdoug> | with less resistance!"