Not Enough Watts
If you are suffering from some issues with your computer/device the root cause could be that your not allocating enough AC/DC power to the device. That is you think your sending 12 Watts to the device but in reality you are actually sending a lot less.
As a result of the device not having enough power you may encounter poor performance with the device and you may mistakenly blame the device for not working correctly. A couple of real world examples of this happening to me:
A few years ago I had a US Robotics modem that wasn't recording phone calls correctly. I checked every possible thing with the modem and couldn't understanding why it wasn't working. I discovered that I actually plug in the wrong power supply into the device, I plugged in a 5 watts power plug where the modem was expecting 8 watts. Once I found the right one everything worked fine.
More recently, I was having problems with my USB Satechi 12 Port USB hub. Every time I plug my iPhone or Amazon Kindle the devices would tell me that there wasn't enough power or the device wasn't supported. Turned out that the problem was I had too many things plugged into my power strip that all my devices were not getting enough power. To solve this, I simply removed the non-essential items and everything now works much better including my iMac Computer.
The life lesson here is that if your encountering any problems with your devices, you may also want to check to see if there's an issue with how much power the device is getting.