[chrisutley]

I have an iMac Core 2 Duo with 2GB or RAM, and the following USB devices:

- Kybd/Mouse (naturally)
- Miglia TV Micro
- HP Printer
- Griffin AirClick
- USB Ext. Drive
- Griffin iMic
- BlackBerry via USB
- iPod
- Griffin iMate

I cannot run all of these at the same time, without some of the devices being rendered useless. I thought perhaps a powered USB hub would help - it didn't. I also tried connecting the TV Micro directly to the iMac, as I figured there were two separate USB buses, and perhaps balancing the load would help - it didn't.

Have I saturated my USB? Is there a workaround? I'm always looking for a way to justify upgrading to a Mac Pro. Would the Mac Pro have greater USB capacity, and if so how much more? Is there a tool that would in real time report on my USB utilization?

[slpdLoad]

Uh, there's no reason you can't run all that. Why didn't the powered hub work? Granted, you might need multiple hubs, but you can run WAY more than 9 devices at a time off of USB.

[disposable]

You can run a total of 127 devices on a single USB, so maybe you have a faulty USB port.

[chrisutley]

Adding a hub is not going to increase bandwidth once you hit the computer, and the 127 device "theoretical limit" is going to vary a great deal based on what kind of devices you have. Try connecting 127 devices to your Mac, let me know how that works for you.

At some point you are going to saturate your USB bus, the question is whether or not the stuff I'm running is capable of doing that. A tool to monitor the load would be most helpful. Hopefully somebody can help me locate one.

[chrisutley]

I capture television and my Sirius feed pretty much 24/7, and then everything else in the USB universe competes for what's left over. I think my hunch that the bus(es) are getting overloaded is probably accurate. I found some references that seem to speak to my problem (see below).

Can anyone speak to the USB bandwidth on the Mac Pro compared to my iMac C2D?

XLR8 apparently offers software with a hub, to monitor load - sounds like my issue is more common than I thought ...

A common USB chain includes a printer, a scanner, a mouse and floppy drive. But since the combined USB bandwidth of all of these devices exceeds the available USB capacity, the simultaneous use of these devices will create problems. The problems can range from a loss of capture quality, to interruption or inconsistent device performance. The IceView’s USB Loadmeter monitors available USB bandwidth and provides feedback via colored lights that alert the user when they approach USB peak or overload conditions. The user can then adjust or expand as needed.

Another tidbit I found in an article about syncing PDA's:

3. Watch out for USB overload. When you have a mountain of data to move, HotSync or ActiveSync can take a considerable amount of time. During these lengthy syncing sessions, it can be tempting to move on to other tasks, such as scanning, printing, or CD burning, while you sync in the background. This is all fine, but keep an eye on which of these other tasks use your USB channel. Spikes in USB traffic, which might temporarily max out your 12Mbps (megabits per second) of USB bandwidth, could cause synchronization errors; conversely, your synching could affect these other apps. To ensure good results, keep your USB traffic during synchronization sessions down to low-bandwidth activities, such as mouse movement.

[bearcatrp]

What is your page in/outs look like with all this hooked up and running?
RaNDY

[slpdLoad]

What exactly happens when you try to plug all 9 of your devices in? You say they are "rendered useless". Does that mean 5 devices work, but when you plug in the 6th they all stop working, or does the 6th one just not work?

[mduell]

Put all your low-bandwidth devices on a hub and put the tv tuner and hard drive each on their own port in the back of the iMac.

[chrisutley]

Originally Posted by mduell 

Put all your low-bandwidth devices on a hub and put the tv tuner and hard drive each on their own port in the back of the iMac.

That's actually how I have it setup right now.

[chrisutley]

Originally Posted by slpdLoad 

What exactly happens when you try to plug all 9 of your devices in? You say they are "rendered useless". Does that mean 5 devices work, but when you plug in the 6th they all stop working, or does the 6th one just not work?

Sometimes the hard drive will unmount, or plugging in my BlackBerry or iPod to sync won't work. Maybe the AirClick stops functioning or EyeTV loses its' feed. In other words some devices continue to work, but which ones fail and in what order is a crap shoot.

[davidwsica]

Did you ever come to a resolution over this issue? I have a similar situation trying to run (3) EyeTV Hybrid units simulaneosly off of my C2D MacBook with one Hybrid hooked directly to one USB port and the other two Hybrids hooked up to the second USB port via a powered hub. I'm wondering also if I need to upgrade to a Mac Pro to get more USB bandwidth.

Thanks, David

[studentmacgeek]

davidwsica,

i'm not too sure that the EyeTV software is actually capable of seeing more than one EyeTV device. I think this because you must choose exactly which device you have when you set up the EyeTV software.

And just out of total curiosity, why do you want to run so many EyeTVs off one MacBook?

[analogika]

Originally Posted by studentmacgeek 

davidwsica,

i'm not too sure that the EyeTV software is actually capable of seeing more than one EyeTV device.

It most definitely is.

You can have several EyeTV devices connected and watch different channels on each. The EyeTV will automatically open a new TV window when an additional device is connected.

Yes, I've tested this.

[analogika]

chris, is it possible that your hub is only a USB 1.1 hub (12 Mbps)?

USB 1.1 had a lower power supply current as well, so if you have USB 2 devices connected, that might explain why they aren't working correctly at some point.

[ginoledesma]

From your device list:

• (Apple ?) Kybd/Mouse -- USB 2.0 for KB, USB 1.1 for mouse
• Miglia TV Micro -- USB 2.0
• HP Printer -- USB 1.1 (not sure what model you have)
• Griffin AirClick -- USB 1.1
• USB Ext. Drive -- USB 2.0
• Griffin iMic -- USB 1.1 (for both v1 and v2 I believe)
• BlackBerry via USB -- USB 2.0 (not sure what model you have)
• iPod -- USB 2.0
• Griffin iMate - USB 1.1

I don't have an iMac C2D handy, so I'm not sure how many USB buses there are and which busses the 3 ports in the rear belong to (Apple System Profiler should be able to tell). Apple's USB developer note doesn't make it clear if each of the three ports has a dedicated 480Mbps channel to the controller. Further aggravating situation is that the single USB controller in the SouthBridge is that it also feeds other internal devices, including iSight, IR Receiver, and Bluetooth. I know in the previous PPC-based iMacs 2 of the 3 ports shared one channel and the other (closest to mini-VGA connector) had its own.

One thing to note is that the presence of a USB 1.1 device will slow down everything in the bus. That's what some "smart hubs" or "intelligent hubs" are trying to solve (see this article for details). I know some of these products (e.g. Belkin TetraHub) dedicate 12Mbps (USB 1.1) per port to prevent bandwidth contention, effectively dividing up the 480Mbps, however. I'm not sure what USB Hub you got, but I'd probably guess it behaves like what's mostly out there in the market -- share the whole bus.

The question that still remains for me is if whether the iMac C2D is capable of giving out 480Mbps to *each* of its ports concurrently, or those three share the same root and have to fight for it (or is 2 are shared and one isn't as before).

Assuming at least one is dedicated, you could do something like this:
Port 1: USB HDD
Port 2: TV Micro
Port 3: USB Hub + All USB 1.1 (HP Printer, Griffin iMic, Griffin AirClick, Griffin iMate, KB/Mouse)

Then, depending on which of these ports are dedicated and which are shared, move the hub accordingly. It'd be tough, I guess, if for example 2 are shared -- that means at least one of the 2 demanding devices won't get all of it.

As for your Blackberry and iPod, since they're something that don't need to be connected most of the time, I'd probably stick them in the USB Hub.

I'd be interested to know what your Apple System Profiler report is on your current USB setup. It'll help reveal if the ports can each give 480Mbps or if they're all sharing it.

Addendum:

I just read from some reviews that the iMic wants (needs?) to be connected to the USB root port instead of a hub, so much so Griffin introduced an "Audio" USB Hub to get around the problem of not having enough ports.

[chrisutley]

Great information, PinoyMac. Thanks...

I will follow-up with the Sys Profiler information ASAP. I also just one-clicked the Belkin hub from Amazon, so I'll report on how that works for me too.

[shinykaro]

Time to get Bluetooth mouse and keyboard.