I nave an iMac which only has USB2 sockets.
All the abailavle portable HDDs seem to require USB3, altough some are reputed to be downwards compatable.
How could I connect one of the si called downwards compatable USB3 druves to my Mac.
Is thre any point in evenconsidering the other USB3 drives?
iMac, OS X Mountain Lion
Note that USB 3.0 is compatible with USB 2.0 ports, so you won't have any problem if you use a USB 3.0 external drive. It will work as any other external drive but with USB 2.0 speed.
There are no problems with USB 3.0 external drives being used with USB 2.0 Macs. A lot of users have this configuration
Which cable must I use? a USB3 or USB2?
If the drive is USB 3 you need a USB 3 cable.
But will a USB cable plug into a USB2 port?
Alternatively, are there any USB2 portable drives?
A USB 3.0 cable fits into a USB 2.0 port without any problem. Both are compatible, as USB 3.0 ports can read USB 2.0 devices but with USB 2.0 speed, and USB 2.0 ports can read USB 3.0 ports but with USB 2.0 speed.
Most external drives are USB 2.0. A quick search will give you a lot of external drives. There are desktop and laptop external drives (desktop external drives give better performance because they include 7200 rpm hard drives, and laptop external drives are usually slower but you can take them everywhere).
I have a LaCie d2 Quadra with FireWire 800, USB 2.0, FireWire 400 and eSATA, and USB 2.0 works without any problem in my 21'5-inch iMac, although I use FireWire 800 because it's faster
Note: this issue is not OS version as it happens with 10.9 and 10.8 and would assume if you can install and older it would do the same.
I just found this out when testing Mavericks with external drive. USB 3.0 does not provide enough power to the decvice. Using a USB 3.0 power hub does the same I think it still tries to get power for the original port.
Work around is using a USB 2.0 hub(powered) to attach the USB 3.0 device.
I think apple knows there are issue and I have yet to find any updates(ie. firmware or recall).
It is a shame thate USB 3.0 data transfer is not available because you cannot get a USB 3.0 disk to stay attached.
Using a USB3 HDD with an iMac
