DSG - Essentially, the engine drives both clutch packs. The outer clutch pack drives gears 1, 3, and 5 (and reverse). The inner clutch pack drives gears 2, 4, and 6. Instead of a standard large dry clutch, each clutch pack is a collection of four small wet interleaved clutch plates. Due to space constraints, the two clutch assemblies are concentric. Because the alternate clutch pack's gearing can be pre-selected (predictive shifts taking place while the other section is in use), un-powered time while shifting is avoided because power is simply switched from one gearbox to the other. The DSG takes about 8 milliseconds to upshift. Compare that to the SMT in the Ferrari Enzo, which takes 150 ms to upshift. The quoted time for upshifts is only the time the engine is completely non-powered.