Mac Pro randomly disconnecting USB devices

You may have too many devices drawing more power from the bus than it can supply, or you may have a faulty device causing the bus to reset. Try connecting everything to a powered hub. If you still get the disconnections, eliminate all devices except the drive, test, then add them back one at a time. Also, check the kernel log (/private/var/log/kernel.log) for relevant error messages.

Unfortunately the hard drive cannot be accessed via a hub.

Then something is wrong with the drive, or the hub, or the USB bus. Boot from your installation DVD and launch Disk Utility from the Utilities menu. Can it see the drive when connected both via the hub and directly? If not, you have a hardware problem. If so, boot in safe mode and test again. If the hub works in safe mode, then you installed a third-party kernel extension that's causing the problem. If it doesn't work in safe mode, you should reinstall the OS. After reinstalling, run Software Update.

Mac OS X: What is Safe Boot, Safe Mode?

Mac OS X 10.6 Help: Reinstalling Mac OS X

Unfortunately the hard drive cannot be accessed via a hub.

Are you using a POWERED Hub for this experiment?

Not being seen when using an unpowered Hub reinforces Linc Davis' assertion that there is not enough power to run all these devices.

This is not an answer. I have this problem with a 6-month-old MacPro. I'm using a POWERED USB HUB for all devices and got this message (and subsequent disconnections of my keyboard and my external hard drive, as I said plugged into a powered usb hub) yesterday when I plugged in my iPhone.

I've read on the web that this is a USB short-out issue and it requires repair (mine would be under warranty). I have a tech conference call this morning to confirm this and plan a course of action. Suggest that anyone having ay issue like this should do the same.

Well, have you solved the Problem? My Waranty is not valid anymore and I've not enough money to buy a new MacPro... Is there a solution without buying a total new machine?

By the way: I also use only powered HUB's and powered external HDD's.

As expected, no reaction...

Readers will add their experience only when they have something to add, or to say, "Me too."

Based on the lack of additional contributions, your problem is not a pervasive problem. That may mean you have a "sample defect". That is a problem that occurs only in your unit, i.e., "it's broke!"

Do you know, for sure, that the power supply is working?

Can the device operate when no other devices are present on the USB Bus?

Yes Grant, I've exchanged the power suppply, cables, the HUB and also the HDD and checked them on my MBP - they work fine. The only USB slot that's working fine is the one on the PCI-E Card. All internal Ports do eject the USB HDD's and also have problem with Printercommunication. I can mount the USB HDD without Problem, until I want to access a larger File or transfer data from or to it, then it ejects itself - well after freezing the Computer for 5min first, until the unmount message appear.

By the way: Sorry, was a bit frustrated. I'm working as an Freelance Editor and really need to have a working USB. But the only thing I found were a huge amount of questions to the same problem, but no solution. And from apple side the only advice was to not use third party device or use only powered HDD's and HUB's. That's not really helpful...

GPJ007: Ok, I hoped to not have to make a new Setup of the OS and all the program. Well in a few weeks there is a gap in the order chain, I'm going to reinstall the OS then and let you know about sucess or not.

Thanks in advance

I have an issue with USB ports on my recently acquired 2011 refurbed 17" MBP.

Twice I plugged in a keyboard and got the notification "device drawing too much power" kind of statement. It's a Bella Advantage series 2 for FCP. Never got that on my 15" '07 core 2 duo.

Just now when I plugged in the keyboard, the laptop disconnected an external usb HD and gave me the same message. Then seconds later the drive reappeared on the desktop.

Bad USB ports? Other suggestions?

Appreciate any advice.

Do you have anything plugged into the USB hub built into the keyboard?

Buy a PCIe USB controller.

Some USB enclosures w/ green drives have a tendency to have trouble copying. There are always threads in the OS X Community that often the external USB drive device is being used for TimeMachine.

USB is just a waste of drive performance when you can install an SATA controller also and use the drive at its full potential. Or try running it off FW800.

ps: this isn't a forum for issues with notebook computers

Hi Kujako, nothing plugged in to the keyboard. I'm familiar with that alert when something requiring bus power is plugged in to the keyboard, but only a mouse plugged in at this time.

It seems to be tied to the keyboard. It happened on two different usb ports with the keyboard when nothing else was plugged in to usb.