Thunderbolt technology is a transformational high-speed dual protocol PC I/O which delivers performance, simplicity, and flexibility. Thunderbolt I/O technology lets you move data between your devices and your computer with 2 channels of 10Gbps flowing both ways (upstream and downstream) at the same time, allowing connecting of up to 6 devices, daisy chained, through a single compact port.
Thunderbolt technology works by having both a PCI Express bus and a DisplayPort connected to the Thunderbolt controller. Simultaneously, traffic from both buses are packetized and transmitted over the Thunderbolt cable to a controller in a downstream device. Full bandwidth is flowing in both directions at the same time allowing more bandwidth and low overhead equaling greater responsiveness. Dual protocols allow for connectivity to more devices and to multi-funtion devices.