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Thunderbolt: 1 Port on Bus-powered Devices

Created on: April 3, 2014
Last updated: August 25, 2015

All bus-powered Thunderbolt devices on the market (from any manufacturer) have only one Thunderbolt port, no passthrough port.

Part of Thunderbolt's spec is that any Thunderbolt port must be able to provide the required 10W of power to any downstream device. Because bus-powered devices do not have power supplies of their own and must rely on the computer or another upstream Thunderbolt device, there is no way to allow a bus-powered Thunderbolt device to provide the required power to a downstream device. The bus-powered device takes the supplied 10W from the computer and uses almost all of the power for itself, leaving a fraction of a Watt.