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Daisy-Chaining USB devices....


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#1
Avicennasis

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I know that regardless of how many USB ports you have, you can add a hub or so.
I also know that most hubs can have additional hubs plugged into them. (so long as they are self-powered.)

Now, the theorical limit on USB daisy-chains is 127 Devices.

I'm curious: Has anyone ever actually attempted/tested this? I've been wondering for a while now, and I figured I'd ask around before I go buy 45+ USB hubs.

Anyone have any info on this?

Edited by Avicennasis, 01 August 2006 - 05:04 PM.

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#2
SRX660

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I have a 4 port usb hub plugged into another 4 port usb hub which is plugged into one of my computers and the setup reads usb flash drives just fine. i needed this setup because i have 5 computers setup on a long desk and needed to be sitting in front of a computer at the other end of the table from where my server was. I did not try using the hub's without them having their own power adapters plugged in. From what i read you can extend a USB cable up to 16 feet without having to have a powered hub.

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#3
Avicennasis

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Well, I understand. USB devices can be powered from the computer.

However, most USB ports put of a max of 500 milliamps. This is devided over the hubs ports. I.E., a USB hub with 5 ports will provide 100 milliamps to each device, providing you have 5 things plugged it.

If you overload this power rating, the computer will shut the port down. This sometimes leads to damage of the port as well.

So, given to basic use, PC-powered hubs are fine. But if you plan to plug a lot of things in at once, it's best to have a self-powered hub. :whistling:



Back to my orignal question: 127 USB ports? Anyone?
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#4
warriorscot

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I think its a theoretical limit based upon the limitations of the OS and hardware, eg XP can only have 4Gb of memory because of 32bit and when they designed it no body though anybody would have anymore than that. Im sure someone might ahve done it but i doubt it its very unlikely anyone actually needs that many USB devices also the overheads would be huge as USB needs a fair bit of processing power it would take a fairly powerful system to comfortably use 127 devices.

45 should be fine but what do you need it for there is probably a better alternative.
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#5
Avicennasis

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I know it's impractical.

I know it takes processing power.

I'm not wanting to do it myself. I'm running perfectly fine with what I have. I'm just curious about this. I've always heard of this theory. I just want to know if it's been tested or not.
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#6
happyrock

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the staff at TECHTV hooked up...if I remember right about 80 usb devices without any problem...it was years ago but I think they ran out of usb devices to connect to the "chain" maybe someone else remembers the show
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#7
Avicennasis

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Figures TECHTV would try it. :whistling:

Anyone? Still seeking an anwser here...
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