USB 3.0 device connecting into USB 2.0 iMac ports

Has the device been formatted as Mac OX Extended (Journaled) using Disk Utility. If not then of course it won't work, most drives come pre-formatted for Windows boxes and need to be reformatted to work with your Mac. BTW, have you considered buying a higher quality enclosure such as a Mercury Elite Pro (www.macsales.com), WD enclosure are not the highest quality and tend to have a high failure rate.

In answer to your question, no. If any updates are available to your iMac you would find them in the Mac App Store and click the Update tab and install all updates.

To format any drive open Disk Utility (Applications - Utilities - Disk Utility) and format the drive. Its an extremely simple process once you have done it 1x.

A USB 3 EHD will work with a USB 2 computer, it just will have USB 2 speed. When it comes to technology a good rule of thumb to remember is any device will be as good as it's weakest link.

To be honest you are over complicating a simple issue, just format the drive and it should work fine. If it doesn't then return it and buy a higher quality device. Also ensure you have good cabling too, if you have a faulty cable then that can cause issues too.

FWIW, seeing it works on other Macs it is not the drive obviously. Try a different cable or a different USB port on your Mac. If neither works try resetting the SMC.

Reset the System Management Controller (SMC) on your Mac - Apple Support

USB 3 is backward compatible with USB 2 - no driver updates necessary. Since you have other Macs that can read the drive the problem isn’t the hard drive. If you are plugging it into a hub try plugging it directly into the computer. (Although there shouldn’t be a problem using a hub it is always good to get all extraneous things out of the way.) Also try an SMC reset. Reset the System Management Controller (SMC) on your Mac - Apple Support Finally, try another cable. USB 3 cables run the gamut from well made and well shielded to horrid and in my experience horrid is more common that well made. If all else fails and the iMac has no trouble with other USB devices, replace the drive.

Totally agree and the OP is correct I did miss his point. My apologies to him.

Reset the SMC (may take 2-3 attempts) and if that does not work then try another USB port and finally if that doesn't work, exchange the cable for another cable.

Totally agree and the OP is correct I did miss his point. My apologies to him.

Reset the SMC (may take 2-3 attempts) and if that does not work then try another USB port and finally if that doesn't work, exchange the cable for another cable.

seagreen939 wrote:

The cable works since it is the same cable I used to connect to the other Macs.

I did try all the steps in the SMC reset, but it did not work. (Thanks for trying! It was worth a shot)

Considering all that you have tried, I would try any EHD and see if the problem is with the drive. I'm assuming the drive has it's own power supply and isn't bus powered. If it is bus powered that could be your problem. iMac USB ports do not output much power and rely on USB devices to have their own external power supply.

There is one possibility. Your iMac is getting up in age and may not be supplying enough power for the drive. Is that one of the portable My Passports?

seagreen939 wrote:

Yes, this is one of the portable My Passport drives.

That is the problem, you need a drive with it's own power supply. If your iMac is an older model they simply do not supply enough power through the USB ports. You can use a powered USB hub if you want or if the drive has the option to plug in a power supply that should work too.