USB3: So near, yet so far - hard drive is seen but not mounted

I have a Gigabyte GA-Z68MX-UD2H-B3 that has Etron EJ168 chips for USB 3.0.

I have my model identifier set to iMac12,2 ... which was the last iMac that did not have USB 3 ports. I'd prefer to stick with iMac12,2 because that Mac's architecture matches this PC (Sandy Bridge), and iMessage works with my serial number that's appropriate for that model.

When I connect my USB3 hard drive to a USB3 port, the computer doesn't mount it. But it does show up in System Information, and if I run "ioreg" on a command line, I see this (which I'll also add as an attachment so it's easier to read):

+-o RP06@1C,5 <class IOPCIDevice, id 0x1000001da, registered, matched, active, busy 1 (7254 ms), retain 11>
| +-o IOPP <class IOPCI2PCIBridge, id 0x10000024f, registered, matched, active, busy 1 (7245 ms), retain 8>
| +-o PXSX@0 <class IOPCIDevice, id 0x1000001db, registered, matched, active, busy 1 (7245 ms), retain 11>
| +-o PXSX@00000000 <class AppleUSBXHCIPCI, id 0x10000026f, registered, matched, active, busy 1 (7227 ms), retain 243>
| +-o AppleUSB20XHCIPort@00100000 <class AppleUSB20XHCIPort, id 0x100000275, registered, matched, active, busy 0 (0 ms), retain 9>
| +-o AppleUSB20XHCIPort@00200000 <class AppleUSB20XHCIPort, id 0x100000276, registered, matched, active, busy 0 (0 ms), retain 9>
| +-o AppleUSB30XHCIPort@00300000 <class AppleUSB30XHCIPort, id 0x100000277, registered, matched, active, busy 0 (0 ms), retain 13>
| +-o AppleUSB30XHCIPort@00400000 <class AppleUSB30XHCIPort, id 0x100000278, registered, matched, active, busy 1 (7227 ms), retain 18>
| +-o USB3.0 Device@00400000 <class IOUSBHostDevice, id 0x10000063f, registered, matched, active, busy 1 (7227 ms), retain 120>
| +-o AppleUSBHostLegacyClient <class AppleUSBHostLegacyClient, id 0x100000644, !registered, !matched, active, busy 0, retain 8>
| +-o AppleUSBHostCompositeDevice <class AppleUSBHostCompositeDevice, id 0x10000064a, !registered, !matched, active, busy 0, retain 4>
| +-o IOUSBHostInterface@0 <class IOUSBHostInterface, id 0x10000064b, registered, matched, active, busy 1 (7221 ms), retain 13>
| +-o IOUSBMassStorageInterfaceNub <class IOUSBMassStorageInterfaceNub, id 0x100000650, registered, matched, active, busy 1 (7094 ms), retain 10>
| +-o IOUSBMassStorageDriverNub <class IOUSBMassStorageDriverNub, id 0x100000652, registered, !matched, active, busy 1 (7092 ms), retain 12>
| +-o IOUSBMassStorageUASDriver <class IOUSBMassStorageUASDriver, id 0x100000654, !registered, !matched, active, busy 0, retain 9>
| +-o IOSCSITargetDevice <class IOSCSITargetDevice, id 0x100000656, !registered, !matched, active, busy 0, retain 7>

The computer obviously sees this as a storage device; why isn't it mounting it?

I have this same problem.

Here's something else strange. I connected a USB2 drive to that USB3 port, and it shows up correctly in System Information as "USB to Serial-ATA bridge" (because this is an internal drive in a USB enclosure.

So, the computer is definitely seeing USB drives that I connect to the USB3 port ... it's just refusing to mount them! And they don't show up in Disk Utility, so I can't mount them manually either.

I tried taking a pair of identical Sandisk Cruzer flash drives, and connecting one to a USB2 port and the other to a USB3 port. The one connected to USB2 shows up as:

Cruzer:

Product ID: 0x5530
Vendor ID: 0x0781 (SanDisk Corporation)
Version: 2.01
Serial Number: 200517399218C251B0E2
Speed: Up to 480 Mb/sec
Manufacturer: SanDisk
Location ID: 0x1d120000 / 2
Current Available (mA): 1000
Current Required (mA): 200
Extra Operating Current (mA): 0
Capacity: 32.02 GB (32,015,679,488 bytes)
Removable Media: No
Detachable Drive: Yes
BSD Name: disk3
Built-In: Yes
Partition Map Type: MBR (Master Boot Record)
Volumes:
32GB A:
Capacity: 32.02 GB (32,015,678,464 bytes)
Available: 32.01 GB (32,007,520,256 bytes)
Writable: Yes
File System: ExFAT
BSD Name: disk3s1
Mount Point: /Volumes/32GB A
Content: Windows_NTFS
Volume UUID: 84FD6651-F37F-3216-A5DB-8C61521231B3

And the one connected to a USB3 port shows up as:

Cruzer:

Product ID: 0x5530
Vendor ID: 0x0781 (SanDisk Corporation)
Version: 2.01
Serial Number: 200517380318C251B0A0
Manufacturer: SanDisk
Location ID: 0x00100000

What could be going wrong here?

There are tons of people that don't have USB 3.0 ports working because only Intel USB 3.0 ports are supported. There is no fix for this at the moment. All we can do is wait.

Are you sure this is the problem? I'd think that if the port isn't supported, the computer wouldn't be able to identify what's connected to the port; but in my case it can see exactly what's connected.