How do you get OSX to rescan the attached hardware

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Level 1

22 points

How do you get OSX to rescan the attached hardware

For some reason, OSX often 'misses' one or more of the attached USB devices during boot-up. It seems to be random and usually can be corrected by rebooting. To make matters worse, I usually don't find out somethings missing until I try to use it which means taking down all running applications before the reboot. In Windows you can go to the device manager and have it 'scan for new hardware'. Is there an equivalent in OSX? It would save a lot of time.

 20" Intel iMac (2.0GB RAM, 500GB HD + 1.5TB external, 20" Cineama Display) Mac OS X (10.4.7) All tools, no talent!

Posted on Jan 15, 2007 6:10 AM

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Answer 1

Kappy

Level 10

362,007 points

Jan 15, 2007 6:52 AM in response to transco

How are the USB devices connected - directly or through a hub? What happens if you simply disconnect the device that isn't detected and then reconnect it rather than rebooting? What type of USB devices are affected?

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Answer 2

lkrupp

Level 7

22,645 points

Jan 15, 2007 7:04 AM in response to transco

To elaborate on what Kappy asked, I had the same problem you are describing and traced it to the D-link USB 2.0 hub I was using. In my case I solved the issue by purchasing a USB 2.0 PCI card for my G5 tower, but since you have an iMac that's not possible. If you are using a USB hub try getting a different kind and see if it helps.

Dual 2.5GHz G5 Power Macintosh Mac OS X (10.4.8) 1.5GB RAM 20" ACD, Linksys WRT54G v6 router

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Answer 3

transco Author

Level 1

22 points

Jan 15, 2007 7:42 AM in response to lkrupp

I've tried 4 different brand hubs with the same result. I hav e a few clues as to what is going on. For example my Bella keyboard will only work plugged directly into the iMac. Even plugging it into the Cinema display's USB outputs fails (i.e. an Apple hub). I have a Wacom graphics graphics tablet. If I leave the pen or its mouse on the pad during the boot process, the tablet usually isn't found. Plugging devices directly into the iMac never fails, but there are only three USB ports. One's connected to the Cinema display and as I said its hub fails just like the others. One USB port is used by the keyboard as explained above. This leaves one iMac port for everything else. Since multiple USB devices must be online simultaneously, no choice but to use a hub. I have found that if I boot up with just the hub attached, then plug the hardware into it one-by-one, this always works. I'm relatively certain that if I could slow down the boot-up port scan (i.e. getting the OS to pause for a few milliseconds between port addresses) it would work OK. Unfortunately I don't know how to do this either.

I see no option other than to use a hub. Now I just need to find some way to get OSX to rescan the USB busses.

 20" Intel iMac (2.0GB RAM, 500GB HD + 1.5TB external, 20" Cineama Display) Mac OS X (10.4.7) All tools, no talent!

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Answer 4

Kappy

Level 10

362,007 points

Jan 15, 2007 7:53 AM in response to transco

Two things are likely problems:

1. Use the standard keyboard that came with the computer.

2. Be sure your Wacom tablet drivers are current.

I'm not familiar with the Cinema Display but why does it need to be connected to the computer's USB port?

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Answer 5

Jan 15, 2007 8:05 AM in response to Kappy

I'm not familiar with the Cinema Display but why does it need to be connected to the computer's USB port?

The Cinema Display has built-in USB and Firewire hubs, two ports for each. I assume that this is the only reason it needs to connect to the corresponding ports on the Mac, although I haven't read this in the documentation. BTW this feature is very handy for my wife's G4 PPC, which only has USB and Firewire ports on the back, and which are a real pain to get to.

Matthew Whiting

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Answer 6

transco Author

Level 1

22 points

Jan 15, 2007 9:31 AM in response to Kappy

The keyboard and graphics tablet were just examples. Everything will fail sooner or later. Yes, all drivers are current.

The Bella keyboad is specifically designed for use with FCP (Final Cut Pro). It's a great time saver when doing complex editing.

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Answer 7

Wade Peeler

Level 6

10,906 points

Jan 15, 2007 10:47 AM in response to transco

I doubt the problem is OS X, as my Intel iMac doesn't seem to have any trouble with the 7 USB devices I have connected through my hub, as well as my UPS and wireless Logitech keyboard/mouse connected directly to the iMac. Are you using self-powered or bus-powered hubs? I can't remember which hub I'm using, but I bought it at the Apple Store. Maybe when I get home I can tell you which one it is.

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Answer 8

Feb 16, 2007 8:00 AM in response to Wade Peeler

I think it is an OS X problem. I'm running 10.4.8, have NO USB hub, but ooting my Mac (G5) occasionally misses my Kensington trackball, which is plugged in to my Mac keyboard. Unplugging/replugging it always resolves it but, as mentioned above, it is a pita. And rarely - very rarely -the Mac will miss my entire Mac keyboard ⚠, needing a hard reset. hmmm....

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