USB question

[joecool]

what's the difference between powered & unpowered devices & ports? i've got a hercules gtxp breakout box with unpowered (i think) ports; they don't seem to work with powered devices (scanner) but do work unpowered devices. this seems bas-ackwards to me - shouldn't powered devices work with unpowered ports & unpowered devices not work with unpowered ports?

inquiring minds want to know ...

 

[bozo1]

First off, many people have reported problems getting scanners and CDROM's working using the GTXP ports, including me.

A powered device is something has has it's own powersource - scanner, CDROM, whatever. An unpowered device is something that uses the voltage on the USB bus - a mouse, a keyboard. An unpowered hub (like the GTXP) doesn't suppliment the voltage coming off your motherboard, it just turns one port into many - all of these devices shared the juice coming off your motherboard and if that isn't sufficient (or too many devices, etc.), you'll have problems. A powered hub has a power source and provides the proper current to each port.

The problem isn't really GTXP specific, many devices have the same problems using any unpowered hub.

 

[Dug]

Try here-
usbman

Here's a small quote-


<< USB Hubs connect to the onboard USB host controller and provide additional ports for connecting USB peripheral devices. A hub does NOT add additional USB bandwidth to the system. Scanners, web cams, digital cameras, card readers and docking bays are high bandwidth devices that are often not properly supported through a USB hub connection. If your USB device is NOT recognized or does not work properly, try connecting it to an onboard port. High bandwidth devices usually require additional USB bandwidth. If you plan on connecting additional high bandwidth USB devices to your computer you will need to purchase and install either a PCI/USB card (Desktop) or USB CardBus (Laptop) adapter to increase the usable USB bandwidth on your system. There is a list of Tested and Approved Hubs and PCI/USB cards in the USB Problem Solver under Tools. >>



There are about 100 troubleshooting tips everywhere. usb is far from perfect. There are too many variables that can effect it. Chipsets, power, os, etc.

 

[joecool]

thanks, guys, that explains it. i'm surprised usb is so flaky - it's been out quite a while now, i thought they finally had all the bugs worked out!

wait, what am i saying, this is PC hardware i'm talking about here!