What just happened to my USB ports?

[GanChan]

I plugged an old external floppy drive into my Mini to look at some ancient files. At some point the USB port serving it stopped functioning -- and so did all the other USB ports, which wouldn't acknowledge any of my external devices. I was afraid I'd fried the hardware, but restarting the Mini seems to have fixed everything.

Even so... what happened? Is it an early warning of trouble to come, or just a weird reaction to an old floppy drive? This Mini is right at the 1-year mark, so the warranty is on the verge of expiring....

 

[Fishrrman]

I will -guess- that the floppy drive was drawing too much "bus power" to operate, and that the Mini "shut down" the USB ports as a result (probably as a protective measure).

I believe there is a trick you can try called the "SMC reset" (serial management controller?). You'll have to search for how to do it, don't have that info at hand as I type this.

Also - go to "System Information" (in the utilities folder) and click on "USB" on the left. What kind of report does it give you?

 

[chogue23]

I think an SMC reset would do the trick, and you can zap the NVRAM while you are at it.

The SMC reset is pretty simple, turn off the machine and pull the power. With it unplugged, hold down the power button for 30 seconds. Then plug it back in while still holding the power button for an additional 15 seconds. Then release and repress the power button for 15 seconds, and then start it up normally. Sometimes this will cause the fans to spin at maximum speed, but that will be corrected after a normal restart.

Resetting the NVRAM is also pretty easy.
Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
Turn on your Mac.
Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
Hold these keys until the computer restarts and you hear the startup sound for a second time. (I do it for a third time for good measure)
Release the keys.

If that doesn't work you may have to run a hardware test to check for more serious problems.

 

[jbarley]

And now for the correct way to reset the SMC.(System Management Controller) Info from Apple support here.
--------------------------------------------------
Resetting the SMC for Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve
Shut down the computer.
Unplug the computer's power cord.
Wait fifteen seconds.
Attach the computer's power cord.
Wait five seconds, then press the power button to turn on the computer.
---------------------------------------------------

 

[chogue23]

And now for the correct way to reset the SMC.(System Management Controller) Info from Apple support here.
--------------------------------------------------
Resetting the SMC for Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve
Shut down the computer.
Unplug the computer's power cord.
Wait fifteen seconds.
Attach the computer's power cord.
Wait five seconds, then press the power button to turn on the computer.
---------------------------------------------------

I do realize that my instructions differ from the ones on the Apple Support site, but there is a reason for that. I was updating multiple computer labs full of iMacs to 10.10.2, and some of the machines would not boot after the upgrade. The Yosemite boot progress bar would stop about half way, even after leaving it on overnight. We tried the method you listed, but it produced the same symptoms. We even tried running a system restore from a flash drive with no luck. I stumbled across one site that suggested the extra steps that would help drain the capacitors and completely reset the power management system, and that was what got us back up and running. If the regular SMC reset doesn't work, this is something else you can try before calling Apple.

 

[294307]

This happened to me last year when I had a USB hub connected to my MacBook Air and I had several devices connected to it (and was being powered by one USB port only). First the hub stopped working then the USB ports stopped working entirely requiring me to restart to get them working again. As Fishrrman mentions, it's possible the USB Floppy Drive was drawing too much power. Sounds very plausible, and akin to the problem I had.

Don't worry, your Mac mini should be fine. If you're in doubt, stop using the one you have right now and get a USB Floppy Drive powered by two USB ports so it can comfortably draw extra power, or one that is externally powered via the AC outlet. I wouldn't know if AC-powered USB Floppy Drives exist as I haven't needed to use a floppy drive in over 10 years!