Mac mini Late 2012 starts USB 3.0 HDDs like USB 2.0 480Mb/sec

Try this:

With your Mac Mini ON and your USB 3.0 drive plugged in, unplug the drive from the end of the cable that is plugged into the drive itself. Leave the cable plugged into the Mini. Wait a couple of seconds then plug the drive back into the cable. Check the results under USB.

Try plugging the USB 3.0 HDD into the Port closest to the Thunderbolt port.

This sounds like the external HDD controller. Is your external HDD in a enclosure and if so what type? I do not think it is the Mini that is the issue. I have had HDD enclosures not work correctly and some do work correctly without resetting (cable on/off/on). On my Mini I have one 3.0 HDD external that works all the time at the correct speeds and another that does not unless I reset.

The ones I usually use are just enclosures that I have installed a hard drive in. I cannot speak to the pre made manufactured ones like WD, etc.

I have a 1TB and 500GB Western Digital USB 3.0/2.0 MyPassport that are both plugged into my Mac Mini for back ups that do not have an issue using the USB SuperSpeed ports. Regardless which port I plug them into they work at 3.0 (5Gb/sec).

I have a Chronos Deluxe 240gb SSD in a Firmtek MiniSwap U3 enclosure on a 2012 MacMini 2.6/i7.

About 20% of the time, the drive appears on the "SuperSpeed" (SS) bus (5gb/s). The rest of the time, it appears on the "Hi-Speed" bus (480MB/s), often with a long time (≈2 minutes) before the drive mounts.

But if I hot-swap a 500gb 2.5" Hitachi Deskstar HD into the enclosure, I always end up on the faster SS bus within seconds.

Power: On the slower bus, I have 500mA available, 100mA required (typical); on the SS bus, I have 900mA available, 36mA required on the HD. I've tried having the enclosure also on its own 5V power adapter, but that makes no difference.

I've tried all ports on the back (with special preference to the one closest to the TB port), and tried attaching the USB cable into the enclosure last. Again, no sure-fire way can be found to get the SSD to consistently mount on the SS bus.

At one point, I thought actually using the TB port for something significant (drawing power) helped things, and I was more consistently on the SS bus then, but that's been debunked.

I even have tried this enclosure/SSD combo on a MBP 15" retina, with flawless SS connections.

Grasping at straws here, as is Firmtek support, who have been very helpful. Anyone experiencing similar issues?

I was having a similar problem with a Startech 4-bay RAID enclosure. Although I could plug an external SDD drive in an enclosure into another USB 3.0 port and for that drive to register as Super Speed every time, no matter which ports the drives were plugged into, the RAID enclosure would always register as Hi-Speed.

However, I had a separate powered Anker USB 3.0 hub (http://www.amazon.co.uk/Portable-Aluminum-Adapter-3-3-Foot-Chipset/dp/B00KMOYFBO /) which always showed up as Super Speed, too, so on a hunch, I plugged the RAID enclosure into that and the enclosure now shows up as Super Speed every time, even though I have several USB 2.0 devices plugged into the hub as well.

did you ever resolve this problem? I'm having an even bigger issue, where the top two items, are listed as USB2 busses and only the third item in the USB tree is a usb 3 bus. nothing I do is making my usb3 hdd work at USB3 speeds!

wondering if you've figured anything out. thanks!