Not sure what the problem is exactly. USB ports on your MacPro are physically connected to a bus. That doesn't ever change. So if you have 2 USB ports that you know are connected to 2 different busses, that's all you need to know, right? Which ports are on which bus can be verified in System Profiler. Plug in some USB devices and check on which bus they show up.

yes, I check on the System Profiler while I plug in two Kinects to see which busses are connected. Apparently, two kinects at the same time on jitter with jit.freenect only be turned on together when they both are connected to USB High-Speed Buses. I have to keep switching USB connector to make High-Speed Bus to Kinect, since Mac Pro appears to allocate USB High-Speed Bus with unknown order.. Sometimes the same USB port is being connected to normal USB Bus or High-Speed Bus. It is a tedious process to make the right connection at the beginning for running the patch. So I have been thinking if an extra USB 2.0 PCI-E card provides more High-Speed Buses to increase the chance to set a right connection for both Kinects. Maybe I am wrong?

This MacPro behavior seems strange. I don't have 1 to verify though. Is it perhaps due to the Kinect driver you're using?

If its a MacPro problem then getting a PCIe card could very well solve it. Make sure you get 1 where each USB port is on its own USB-bus. Cheaper cards will have 1 shared USB-bus for all the USB ports on the card.

I have this firewire+usb card that has separate busses for each port. The usb ports never worked on my hackintosh though. You might have more luck with your genuine Mac. http://sonnettech.com/product/tangoexpress800.html

Out of curiosity, are you extending the Kinect's USB cable? If so, how?

thank dtr. I need to try an extra USB2.0 PCI-e card.

when I need to extend the length of Kinect's USB cable, I use a USB repeater cable. of course with the kinect power adapter.

Slightly O/T I want two kinects as well but I haven't got a PCI-e card slot (2011 MBP).

I'm not actually using the rgb feed, just the depth cam - if I disable the rgb (I'm not actually sure you can do this with jit.freenect?) would that mean I could use 2 kinects on one usb bus?

Anyone know if jit.openni works with multiple kinects?

I haven't actually got the 2nd kinect yet but it'd be good to know.

The reason I asked is that you need to use an active repeater to support the high speed/power requirements. If you're not using an active repeater this could be the cause of your problems. Active repeaters are available up to 25m.

Here's an example of an active repeater cable: http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10303&cs_id=1030312&p_id=6149&seq=1&format=2

For long extensions up to 100m I use a CAT5x converter - here's one that I've used that works perfectly. http://www.blackbox.com/Store/Detail.aspx/USB-2-0-CATx-Extender-1-Port/IC253A

^ Probably this.

There should be no problems connecting to different busses on the MP, provided they are separate full-spec (inc power reqs) USB Hubs, and I would presume the MP has at least two if not more.

Obviously, hubs (busses) != ports . . . which I'm sure the OP understands, just mentioning for completeness.

Yes, Jesse. That USB repeater is just like what I am using. I only need 20m, and it ables to connect kinnect to my Mac Pro. It is just sometimes difficult to be allocated with USB High-Speed Bus. It its usually be connected to a normal USB port. I don't understand why Kinect only works with High-Speed Bus though.

It's because of the data rate of the Kinect itself. It's very odd to me that the Mac Pro would not connect at USB 2.0 speeds to the Kinect at all times if the cabling is right. Have you seen this behavior with the Kinect directly attached to the computer?

AFAIK all of the USB ports on a Mac Pro are USB 2.0 capable. If the system profiler is showing ports running at USB 1.1 speeds then that could be due to incorrect negotiation on the USB bus between the computer and the device itself.

this happens both Kinect with and without the repeater. I see all devices are running in USB 2.0 though.