Problem in Using two USB Camera Simultaneously

When We Tried to Use Two Camera Simultaneously at a time for stereo-vision , the real problem occurs 
when the camera all appear in the device manager but only one camera will work at a time.
This is probably the Camera Driver problem which could not support total bandwidth of dual camera. We managed to solve our problem in windows Environment but could not. So we decided to migrate to Linux(Ubuntu 10.10) and fortunately Ubuntu had inbuilt Driver for PS3 USB camera which supported dual camera.
I will show use the reason mathematically why two USB camera were not supported simultaneously.

Total Bandwidth of USB 2.0=480Mbits/sec
Bandwidth of single USB Camera = number of channels*total bits*resolution*frames
per sec
=3*24*640*480 *15
=3317760000 bit/sec
=331.776Mbits/sec
Hence bandwidth of single camera exceeded 50% of the total bandwidth of USB 2.0. Also the
USB Ports on laptop are on the same hub and they share same common resources
(bandwidth). Also the Driver of PS3 Eye cam (USB Webcam) did not support the dual camera
even at minimum resolution and minimum frame rates per second.
With two identical USB cameras, the hardest thing is to make them work together
simultaneously. In some cases, camera drivers don't allow/support viewing both cameras
simultaneously - one might watch one camera or another, but not both.
Fortunately Ubuntu 10.04 and newer version had inbuilt support for PS3 Eye cam Driver and
supported the simultaneous running of dual USB camera.

Dual PS3 Camera mounted Mechanically