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USB power requirements

 
 
darkkael
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      03-14-2005, 01:29 AM
Dear group,

I'm experiencing a number of system failures that look to be the result
of overloading the USB ports with too many devices. Is this even
feasible? Are there limits to the power you can draw down a single
motherboard? What is the limit if there is one?

Are there resources where i can find more information?

Thanks,

S.

 
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Emile Jackson
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      03-14-2005, 10:48 AM
Hi,

Off course there are limitations to the amount of power you can draw
from a motherboard. First of all there is the limitation of your PSU.
But if your Power Supply is heavy enough, the system can also freeze
or go out when the motherboard gets to hot.

It has a reason that many USB devices have a power supply unit of
their own, like 3,5'' external hard drives, scanners and such.

According the USB specifications the USB port should supply max. 500mA
to every USB device at 5V. This means a device on a USB port can
consume 2.5 Watts.

Many computers these days have a 300W or 350W power supply, which is
often nearly enough to keep the system running. When you connect 6 USB
devices without a power supply of their own (which is possible these
days on many motherboards), you draw another 15 Watts from your
system. So in an extreme case, it is very possible your system will be
unstable because of that.

More info on USB specs and design is here:
http://www.usb.org/developers/usbfaq/

I don't know how many things you are trying to connect, but also keep
in mind that one of your USB devices, or the driver that controls it
can be malfunctioning.

Regards,

Emile

"darkkael" <(E-Mail Removed)> wrote in message news:<(E-Mail Removed) oups.com>...
> Dear group,
>
> I'm experiencing a number of system failures that look to be the result
> of overloading the USB ports with too many devices. Is this even
> feasible? Are there limits to the power you can draw down a single
> motherboard? What is the limit if there is one?
>
> Are there resources where i can find more information?
>
> Thanks,
>
> S.

 
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darkkael
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      03-15-2005, 12:46 AM
Thanks for the info.

Most of the devices plugged in to the USB are self powered, i wondered
if they were drawing some additioanl power from the motherboard
regardless of this fact.

I have at most 3 unpowered devices and 7 powered devices.

I'm setting up some test hardware tomorrow to try to replicate some of
the problems

S

 
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darkkael
Guest
Posts: n/a
 
      03-15-2005, 12:46 AM
Thanks for the info.

Most of the devices plugged in to the USB are self powered, i wondered
if they were drawing some additioanl power from the motherboard
regardless of this fact.

I have at most 3 unpowered devices and 7 powered devices.

I'm setting up some test hardware tomorrow to try to replicate some of
the problems

S

 
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