If I connnect my monitor via VGA-USB connector using a USB Hub instead of connecting it directly to my laptop - would the preformance be affected? (See Links to products I have)

Posted on 2009-12-18
Medium Priority
Last Modified: 2012-05-08
Products I bought:
USB Hub:


Would you recommend that I connect the' VGA to USB' connecter directly to my laptop (Thinkpad T400) or would it be okay to connect it to my powered USB hub?

I would prefer connecting it to the hub but dont want to see a drop in performance. Do you guys expect a drop in performance if I were to connect the monitor using the hub and not directly to the computer?
Question by:darthvader747
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Expert Comment

by:Jon Brelie
ID: 26084083
In my experience, this almost always has a negative impact, but I've never used the devices you listed.

Also, the 'negative impact' is usually only noticeable when I am playing a game.  (ie: slower refresh... lack of crispness)
LVL 70

Expert Comment

ID: 26084786
As long as it's a powered hub (be sure you're using the AC adapter to power the hub)  there's no difference in the bandwidth UNLESS you've got multiple devices attached to the hub -- in which case the devices on the hub have to share the bandwidth for that specific USB port.

In general, I'd recommend attaching the video adapter directly to one of the laptop's USB ports, and connecting your other devices through the hub, as the video adapter is likely the most bandwidth-intensive device you're using.

Author Comment

ID: 26084976
Okay! Thanks.

Now I am curious to know if I attach 6 devices to a USB port (hard drives, printers etc) do each one of those devices get 1/6th of the bandwidth of the USB port (ie- The one to which the USB hub is connected)?

This would imply that connecting multiple devices through a USB hub and using them simultaniously will slow things down significantly!!

If I am doing data transfer between 2 external drives, I am best to connected them to separate USB ports on the computer and not to the hub. Correct?

How much bandwidth does a single USB port have?

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Accepted Solution

garycase earned 2000 total points
ID: 26085061
No, they don't each get 1/6th of the bandwidth -- they get whatever they need up to the limits of the port's bandwidth (which is 480mb/s).     But if a device doesn't need 1/6th (e.g. a printer, mouse, etc.) then it doesn't "waste" that bandwidth.

Yes, it means that if you connect a lot of high speed devices through the same hub you can slow things down -- e.g. copying data between two hard drives on the same hub will be slower than if they were attached to independent ports.

Note that the theortical 480mb/s speed is rarely reached -- in practical use you'll typically get about 2/3rds of that (e.g. 320mb/s).

For MOST applications, you'll find that connecting through a hub is fine -- even disk-disk transfers will still be reasonably quick (unless you're copying huge amounts of data).    What I suggested above is that a video adapter is not only bandwidth-intenisve, but is a device where bandwidth bottlenecks are very visible, since you're watching the display.    So for that use I'd definitely try to attach it directly to its own USB port.

Author Closing Comment

ID: 31667944
Very nicely explained. Thanks!

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