iMac, Leopard - Inconsistent experience with USB

[Rob Veteran]

So I've got an Intel iMac, three USB ports on the back. I'm also using an external display, a Dell 2005FPW monitor which has 4 USB ports on it. So we have a cable running from one USB port on the iMac to the Dell, acting as a hub.

When I start the machine up, for some reason none of the devices attached to the Dell monitor function, until I disconnect and reconnect the cable connecting the iMac to the hub. Then the devices spring into action, running at full USB 2.0 speed. I don't recall having this problem before about 2 months ago, when perhaps I changed some kind of power management setting? A pure guess.

Placed in the Software section here at Neowin but could easily be a Hardware problem - will move if someone can clarify :) Thanks in advance for any help. And to those who have seen this retweeted from my feed, you can find a link to my profile in my signature to reply there.

[robthecomputerguy]

Rob,

It could absolutely be a hardware problem, but what I do know from working with a bunch of different Dell monitors is that the hubs are powered on or off with the power of the monitor itself, so if you were to wait to turn on your Dell monitor until after you arrived at the OSX desktop, I would bet that your devices would all appear.

I had a similar experience with a hard drive just yesterday and I would tell you that it was a FAT hard drive, not a GUID hard drive, and I was able to reproduce it. As long as I disconnected the USB cable from the computer and reconnected it, the computer saw the hard drive just fine. But booting with the hard drive already connected was a no-go.

So, for that matter, does turning the monitor off and on again help get the devices recognized?

(It's been my experience that turning the monitor off also cuts power to the hub, but I have not personally handled a 2005fpw so I could be wrong in your case.)

I'll be curious to find out if it's something completely unrelated to anything I'm proposing here.

Rob

[Rob Veteran]

Hi Rob, thanks for taking the time to respond, and even to register to respond by the looks of things!

'Hard' turning the monitor off, i.e. at the electrical mains, and then powering it on after OS X has booted does indeed work, and seems to have the same effect as disconnecting and reconnecting the USB cable. However if I merely turn the monitor off via the switch on the front, and then turn it back on again, it has no effect. That said, if the USB hub is already functioning (after I've disconnected and reconnected the cable from the iMac), 'soft' powering off the monitor keeps the attached USB devices powered and fully functioning.

[robthecomputerguy]

Eeek! I can't even plug my ipod into my dell monitors because if the monitor goes into power saving mode it cuts the charging to the ipod, which I find completely absurd.

You haven't itemized what you have connected to the dell's hub, but if you connected one item at a time and tried every possible combination, I bet you could figure out that one particular peripheral is causing the group to not get auto-recognized.

I'd bet it was a hard drive. But I'd also bet that more than one combination could get that hub to fail. The Dell hubs in the monitors are just disappointing... and I personally think from my observations over the long haul that using the power saving features really make a long term difference in the monitor's life, so I'm not about to turn off the power saving features.

I'm not sure why they bothered to put FOUR usb ports - mind you, 2 underneath in the back, right? (All mine have 2 ports completely out of the way in the back) --- that power off as soon as I leave my monitor for 15+ minutes... seems absurd to me.

But I'll also add that I have tried NUMEROUS brands of powered USB ports and I believe that more than one brand failed on me and destroyed different equipment. I mention this only because I think this technology with powered hubs is an issue. I now run a hackintosh with 10 USB ports so I actually don't have to routinely use a hub at all anymore. If your device has its own power source, then the hub theoretically doesn't need to be powered.... but my point is just that powered hubs are tricky.

I organize my USB cables such that if I have to use a hub I use a non-powered 4 port hub, and for anything that won't work with that 4 port hub, I use a long enough USB cable to connect that item directly to the computer. I just avoid powered hubs at all costs. The last hub fried my printer that I love dearly and I just won't take that risk again.

Rob

[Rob Veteran]

You know I think you might be right about it being a hard drive. But in fact, I keep the external hard drives powered off until I need them, so they shouldn't be interfering. You're also right about USB hubs in general - I hate the things, had nothing but trouble, but at least on Windows I found the Dell monitor, being self-powered, to function pretty adequately. But something's just causing trouble here.

Connected to the Dell are an Apple dock (side of monitor), Freecom external USB drive (side of monitor), USB Audio Interface (bottom of monitor) and Seagate external USB drive (bottom of monitor). I would agree that some of these ought to be connected directly, but I believe it was when I was having issues with my keyboard being recognised that out of sheer frustration I plugged the mouse and keyboard directly into the iMac and everything else on the hub. Out of all of those devices though, the two most likely to work would be the low-powered peripherals!

I think it could be the USB Audio Interface. Let me power that off and reboot the machine, and see if the dock works without having to dis/reconnect.

[Rob Veteran]

Success! Looks like it was an overload of high-power devices on the USB hub, specifically a HDD and the USB Audio Interface. Shifted them around (was sure I had tried this before but perhaps kept the USB Audio Interface there) and now things seem to be loading properly. Many thanks.

When I think about it now, it seems such a rookie mistake. Suspect it was a case of 'this is the only free port, plug it in regardless' without thinking. Oh well :)

[Subject Delta]

Not a fan of USB hubs myself, prefer to get my extra ports via a PCI card.

[Guest]

I've had similar problems with the Apple keyboard USB ports, they are only good for low-powered devices. The lack of USB ports on the iMac are one of its weak point :(.

[Elliott]

I have a MBP with an Apple Cinema Display and a powered Belkin hub. My MBP ports and my ACD ports have no problem with anything, but my Belkin hub will sometimes drop out if I connected another peripheral to it (say, plugging in my iPhone). One time, it corrupted my backup drive during a backup.

Moral of the story: most USB hubs suck. :p

[Rob Veteran]

Unfortunately I was too hasty in proclaiming success - the problem reoccurred this morning when I rebooted the machine. Said it couldn't find a mouse or keyboard (no LED lights on them either) until I disconnected and reconnected the monitor's USB cable. Any other suggestions?

[robthecomputerguy]

Hmmm if you go into "About this Mac" and "More Info" ... can you grab a screenshot of the detail box where the hub is displayed?

I have a feeling this is a "wrongly" designed hub, that although it appears to have power, it is really acting like an unpowered hub.

Although if I look through other notes on Dell monitors, the two on the side are supposed to be low power and the two on the back are supposed to be full power, but you'll have no way of seeing that via the "about this mac" screen - and that may be exactly where the gap is that causes this incompatibility of sorts.

Now based on my preceding paragraph, one would connect hard drives to the side, and audio and hub to the back. Keyboard and mouse would be on the back too. Anything with it's own plug would go on the side....

If you were to follow that rule, that you only use items with their own plug/power on the side, does that make the problem any better?

Rob

[Rob Veteran]

Unfortunately no; everything that's plugged into the monitor is entirely unpowered and nonresponsive until I disconnect and reconnect the upstream/downstream master USB connection to the iMac.

We currently have:

iMac - USB port 1 - connection to Dell 2005FPW

iMac - USB port 2 - M-Audio interface

iMac - USB port 3 - Freecom HDD

Dell - USB port 1 (side) - Mouse

Dell - USB port 2 (side) - iPhone

Dell - USB port 3 (underneath) - Seagate HDD

Dell - USB port 4 (underneath) - Keyboard

Dell - Upstream USB port to iMac.

And the screenshot you requested: http://qkpic.com/fad71

[robthecomputerguy]

well, let's see... There's something to be gleaned from that "available" and "required" mA numbers..........!

[Rob Veteran]

The hub says it has 500mA available ... if the iPhone is unplugged, the 100mA each required by the peripherals would only make 200mA out of the 500mA available, yet none of the devices are powered upon boot :(

[robthecomputerguy]

I think you have truly proven that there is an incompatibility here - I think the power is just inconsistent... We could juggle and experiment, but I don't think any of that will help you solve the problem. I think either the Mac or the Dell is adjusting power incorrectly based on signals it's getting through the usb line. I don't think it's THAT intelligent, but some kind of signaling/switching simply isn't functioning correctly here.

What you do need to do is connect an unpowered hub to the back of the iMac, and just go with something that will be not-unsightly. That will spread things out enough that you can just connect things however most convenient for you.

Stay away from Belkin entirely - Linksys and IOGear are good bets. Newegg.com is a good resource for sensible product reviews.

[Rob Veteran]

Thanks so much for your continued help here! Have tried one last attempt at fixing things by plugging the monitor into a separate power socket compared with the power strip the rest of the devices are in. Could be that it's simply being underpowered? Will let you know!

[robthecomputerguy]

Well the answer is yes!

But your computer would still always keep the power it needs for itself first and power the hubs last....

[panicswitched]

i had a similar issue with a 1905wp, usb ports in them suck it died after a week and never worked again lol

[Rob Veteran]

Didn't work - same issue when I turned it on. Pain in the arse.