At 08:56 PM 1/3/2010, Harvey wrote:
>I recently bought a Canon CanoScan 8800F scanner and it supports Hi 
>Speed USB 2.0.  I connected it to my computer a AMD GA-M57SLI-S4 
>motherboard. When I turn on the scanner I get the message "This USB 
>device can perform faster if connected to a Hi Speed 2.0 port."
>How can I tell the speed I'm running at? Since they say that the Hi 
>Speed runs 40x faster then USB 1.1 there would be a major difference 
>in performance.
>The motherboard manual just says it supports 2.0/1.1. The Hub I'm 
>running it through supports Hi Speed 2.0 and is self powered.

Hi, Harvey

It is my understanding that it all depends what else you have 
connected to the hub. If one single device is running at 1.1 speed, 
ALL the devices connected to the same hub will fall back to 1.1. So, 
although your USB 2.0 is capable of transferring raw data rate at 
480Mbps, you might be actually down to a 12Mbps (or less). Since I 
have some old (but fully functional devices) I have separate 
exclusive hubs for 1.1 and 2.0.

Also, a USB hub has to re-calculate the time left before the next sof 
(end of the uframe); the small extra delay added by the hardware hub 
could make the transaction not handled as fast as a device directly 
connected to the host. If several devices are connected on the USB 
hub and working in parallel (for example, a webcam + a USB flash 
drive + a mouse), then the USB bandwidth is shared among the devices 
usage. USB hub ports are not as capable or flexible as real PC ports 
so you can't expect top spec performance from them.

When I built my PC I made sure that I had oodles of internal USB and 
FireWire ports (8 and 3), so that I can connect critical external 
devices (like hard-drives) directly to them.

USBInfo & SiSoftware Sandra can report your USB speed status.

Hope this helps.

Andrew



>HarveyRose
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Andrew J. Rozsa
Indian Springs Village Alabama USA
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