Originally Posted by
Background Noise
My real question was not about that end of things but whether you could draw power (and/or how much) from a pci slot, ie how does the power get from the MB to the usb socket using one of these pci-based devices.
The PCI slot on the motherboard has its own feed from the power supply. The PCI USB card uses that to feed the USB sockets.
Given that a graphics card can be fed off a PCI slot, and given the power consumption of some graphics cards, I wouldn't expect any problem with USB. I've not seen a PCI USB card with any restriction on the power that can be taken from the USB - other than the standard "500mA per socket".