Under Mavericks, The System Report for USB Current Required (mA): for a WD external drive was listed as 248. Under Yosemite 10.10.1, this same parameter is listed as 896 for the same drive (curiously a factor of 4 increase). Which of these values is correct? if the 896 mA value is correct, then the WD drive is coming dangerously close to the 900mA max for a USB 3.0 port.
iMac (21.5-inch, Late 2012), OS X Yosemite (10.10.1)
Most 2.5" hard drives run on 500mA, anything more is out of spec. Which WD drive do you have?
The MacOS will tell you if the drive attached to the USB port is using too much power, otherwise, I don't see much of a need to worry about it.
Chattphotos, thanks for the quick reply. The drive is a Western Digital 1 TB My Passport for Mac. You are probably right not to worry about it. However, it does concern me that the same drive under Mavericks was reporting 248 mA (which seems correct to me) and under Yosemite it is now reporting 896 mA which seems too high. I think the two versions of the OS should at least be consistent in reporting this parameter. It is hard to get WD to state the current requirements for this drive.
Sorry. there was an error in the original post: Under Mavericks, The System Report for USB Current Required (mA): for a WD external drive was listed as 248. The 248 for Current Required (mA) should have been listed as 224.
System Report USB Current Required
