Why can't I connect more than 4 USB devices?

February 22, 2011 at 11:08:05
Specs: Windows XP, 2200+/4GB
Why can't I connect more than 4 USB devices? Mouse, keyboard, printer and 2 external HDs. Running WinXP with all patches. After connecting the 4th device the 5th never works or that one will work and one of the other devices stop working.

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#1
February 22, 2011 at 11:43:57
External hard drives, external optical drives, and any other type of USB adapter that connects a hard drive or an optical drive to a computer, requires that the USB port that they connect to must be able to supply the full max 500ma per port the USB specs allow for.

If you connect a USB device to a port in a multiport external USB hub that connects to only one USB port on the computer, ports in USB hubs DO NOT work with everything, even when the hub is a "powered" hub - has an external power supply connected to it. If that type of external hub is NOT "powered" the total amount of current that all the devices connected to the hub can draw can never be more than 500ma if you want all the devices plugged into it to (possibly) work properly.

Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1:
http://www.computing.net/answers/ha...

Check that out first.
......

Rarely, not all the ports on the back of a desktop case may be able to supply 500ma each.

If you have a desktop computer, Note that I answered a Topic on this site where a guy had an external drive, which does require the full 500ma, connected to a port on the back of a desktop case - it would not work properly when a webcam was in the port next to it, but it worked fine when the webcam was unplugged. Ports on the back of a desktop case often have two ports connected to the same USB controller module that are ports one above the other - you could try connecting the cable to one of those and leaving the other un-used.
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#2
February 22, 2011 at 12:16:06
Thanks. I read most of your earlier posts. The 2 HDs are powered via wall plug (WD external drives) and are not powered via the USB port. Printer is enternally powered. Keyboard, mouse, USB hub internally mounted (3.5in bay), USB SD card reader, USB memory sticks....all powered via USB bus. I have a wall-powered USB hub; why doesn't this alleviate the problem providing power to the devices? It seems there is no working configuration past 4 devices!

Do the externally powered devices pull 100ma even if they are externally powered (HDs, printer)?


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#3
February 22, 2011 at 12:20:12
IMO, it's stupid to tie up USB ports with a mouse & keyboard. If your motherboard has PS/2 ports, use them.

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Related Solutions

#4
February 22, 2011 at 12:22:34
I agree....not my 'puter....my stepson's!

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#5
February 22, 2011 at 12:24:38
Do the externally powered devices pull 100ma even if they are externally powered (HDs, printer)?

Some do, some don't

If you go into device manager and look under USB controllers > USB Root Hub it will tell you how much power each device is drawing.

Stuart


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#6
February 22, 2011 at 13:25:10
"The 2 HDs are powered via wall plug (WD external drives) and are not powered via the USB port."

The USB connection must still be able to supply the full 500ma for external drives that use 3.5" drives.
3.5" drives require both 12v and 5v power and they draw a lot more than 500ma total current and more than 500ma at 5v. 2.5" drives require only 5v power. The USB connection supplies only 5v power.


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