Depends on how much power your Hard Drive uses.
From spending an insane amount of time researching the topic, it seems people who us USB powered hard drive falls into 3 groups.
1. Single cable seems to work just find for them. I Find people who report this usually have a smaller storage size (Less or equal to 500Gb), but this is just off memory not like I actually created a statistic for it....
2. Single cable works, as in the Wii U recongizes it and formats it.
However game freezes now and then or crashes. I'm not sure if people are confused by the crashes inherent with playing the Wii (fixed by the recent patch) or it actually crash due to the hard drive.
3. Y-cable fixes everything. Or have the same diagostic as group 2. Again I'm not sure if people are confusing the game crashes due to the system *(Fixed by the recent patch) or its actually crashing due to the hard drive.
I fell into group 3. I was extremely relieved since I thought I just blew $90 on a hard drive that doesn't work.
I have then downloaded and played Nintendoland for about 1 hour with no problems or slowdowns. Moved Trine 2 over and it played just as well as when it was on the consols hard drive.
Edited by currysonic, 06 December 2012 - 03:04 AM.