Do not cascade hubs beyond four levels on either SPARC based or x86 based systems. On SPARC systems, the OpenBootTM PROM cannot reliably probe beyond four levels of devices.
Do not cascade bus-powered hubs. (Plug a bus-powered hub into another bus-powered hub.) A bus-powered hub does not have its own power supply.
Do not connect a device that requires a large amount of power to a bus-powered hub. These devices might not work well on bus-powered hubs or might drain the hub of power for other devices. An example of such a device is a USB diskette device.