The Thunderbolt adapter 840 Pro Also with me is 520 GB on a Macbook Pro 17 "OSX 10.8.4 problems with a Samsung. Normal files could be first transferred easily fast. eg. 116 GB in 7 min. Then problems occurred with interen Apple programs on eg. Time Machine, Formatting, Data Migration, often NO GO! I also do not believe in a power, but possibly at a OSX problem After my recent knowledge is neither an OSX nor a power problem, but obviously at a heat problem that occurs at longer maturities, and thus a higher temperature. Therefore, initially fast data transfer with any problems later. By plug position of TB adapter and slim form factor of 840, the disk can be installed with a 4mm gap. Thus, the direct thermal conduction between the two devices is prevented and it can be achieved by the addition better air cooling for both units, a smaller, problem-free temperature. This especially in a vertical mode. Since my 840 500 GB works absolutely flawlessly, even during prolonged use.