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Is there a limit to the number of USB devices in Win 7?

Last response: in Windows 7
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May 27, 2012 10:57:43 AM

my rig is

ASUS Rampage iii Formula Motherboard
Intel i7 960 @ 3.2 GHz stock
Corsair H70 cooler
12GB of Corsair Dominator RAM
EVGA GTX 570 HD 2.5GB

So I record music on my PC and have 2 guitar pedals and a synthesizer running to my computer via usb 2.0 to utilize their midi features. For some reason though when I have all of these devices on at once, one of the devices keeps disconnecting and reconnecting over and over again. It's driving me crazy. I switched out the usb cable for the device and same thing.

I got a nzxt iuo1 usb expansion hub to open up some of my usb ports for future use. I don't know if this could be causing the problem because the hub itself draws its power from a psu molex header. I have the hub plugged into one of my motherboards usb headers. The hub has two flash drives and the front panel usb and card reader panels plugged into it.

On the back of my tower at the motherboards I/O port, I have these items plugged in through USB; mouse, keyboard, GNX4(guitar pedal), GR-55(guitar pedal), MO6(synthesizer), and an xbox 360 wireless reciever for gaming.

Do I have more devices plugged in than Windows 7 can handle?
a b $ Windows 7
May 27, 2012 11:46:28 AM

There is a limit but it's pretty massivie.
I'm thinking, like 127?
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a b $ Windows 7
May 27, 2012 12:03:29 PM

Universal Serial Bus Wiki
under System design:
"Up to 127 devices, including hub devices if present, may be connected to a single host controller.[14][15]"

You might be running into issues with the amount of power that can be delivered to all devices.
When you simplify the amount of USB devices attached does that problem device still have trouble staying connected? How about when it alone is connected?
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Related resources
a b $ Windows 7
May 27, 2012 12:06:33 PM

Cuzzin Chizzy said:
one of the devices keeps disconnecting and reconnecting over and over again.
What device is giving you problems?
Is there any history of that device causing others the same type problem? Any chance that device is malfunctioning on it's own?



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May 27, 2012 12:16:58 PM

I'm running a MO6 and a digitech GNX4 through USB and I can run either of them or both at the same time no problems. I can run the GR55 by itself with no connection problems but if one of the other devices is on(mostly the GNX4) I get a constant disconnect/ reconnect sound in Win7. This problem haunts me in my sleep.

I've turned off all power saving features for USB. Hmmmmm.... ? :( 
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May 27, 2012 12:19:13 PM

WR2 said:
Universal Serial Bus Wiki
under System design:
"Up to 127 devices, including hub devices if present, may be connected to a single host controller.[14][15]"

You might be running into issues with the amount of power that can be delivered to all devices.
When you simplify the amount of USB devices attached does that problem device still have trouble staying connected? How about when it alone is connected?


Well the GNX4, MO6,and GR55 are all self powered, that is, they have their own power cords for a standard outlet. The mouse, keyboard and 360 wireless adapter are all powered through usb.

Then the two usb drives, which are software license drives, card reader and usb panel are all connected to the usb hub which is powered from the psu.
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a b $ Windows 7
May 27, 2012 12:28:14 PM

With the devices being independently powered it's looking more like there might be some signaling issues between some devices and the USB hub.

I think you're going to have better luck looking in support forums for the devices you use.
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May 27, 2012 12:42:07 PM

I have been. One guy said that it might be that my gtx570 is eating up all my irq bandwidth or something like that. Could that be it?

To quote him "Avoid USB ports on PCI cards, (and do not use an external USB HUB!) - on many motherboards, the PCI bus can become swamped when the Video card is set with a too high frame rate. Most times, Game Machine PC's with super fast video cards make terrible DAW platforms due to starving PCI bus."

That a valid point?
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a b $ Windows 7
May 27, 2012 12:59:46 PM

Probably not valid as I read the X58 block diagram.

The PCI Express Graphics 2.0 has it's own connection to the Northbridge.
And I'm pretty sure it doesn't share the interrupts on the PCI bus.

And probably not valid about using external USB Hub.
But I also can't rule it out as being possibly true.
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a b $ Windows 7
May 27, 2012 1:18:54 PM

If you're wondering about the missing PCI bus on the block diagram it's because it's 'tacked on' since the basic platform does not require a PCI bus. They're added on by the motherboard manufacturers for backward compatibility with some older hardware.
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a b $ Windows 7
May 27, 2012 1:44:57 PM

What kind of external PSU's are you using with the music interfaces that you have, are they linear transformer type (large and heavy (makes a AC-line buzzing noise when held close to ears)) or switchmode (small and light(silent)), with multiple switchmode type supplies connected up sometimes you can get strange oscillation types of interferance whether they be fixed or floating ground types, try a universal regulated psu with the equipment the disconnects and re connects to see if it sorts the problem out.
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May 27, 2012 3:21:38 PM

Ok so I downloaded a program called Plug and Play monitor and I could see that a USB device was disconnecting/reconnecting but couldn't understand the code so didn't help much. I was trying to see which item was disappearing/ reappearing in the device manager but nothing on the list was gone for a perceivable amount of time.

Finally I went into my Devices and Printers screen to see if there was some kind of option I was missing that could fix it, and I saw that when the "ba-dunk" sound happened, the GR55 flashed as if disconnecting and reconnecting really quickly.


So starting with that as the problem I realized that it was in the USB slot right next to the 360 wireless adapter(which is powered by the motherboard through usb) so I figured I'd try moving the GR55 to one of my open usb3.0 slots. It was working without disconnect. OK now we're getting somewhere.

For reference
http://i1148.photobucket.com/albums/o576/CuzzinChizzy/R... USB port layout
http://i1148.photobucket.com/albums/o576/CuzzinChizzy/r... How my setup is

So I figured I would try to unplug the 360 wireless adapter and plug the GR55 back into its old home to see if it worked right without the 360 adapter drawing power right next to it. IT DID! Once again the GR55 was connected without the disconnect problem.

I thought "the 360 wireless adapter is the problem" so to verify that. I plugged it back into it's old home in the USB slot next to the GR55 expecting the disconnect problem to be back. It did not come back, at least yet.!??

The only other thing I noticed is that those two usb ports (1 &2) that the GR55 and wireless adapter were plugged into seemed kinda spacious. The USB cable seems to have more wiggle room in those ports. Maybe I need some fatter cables.

Thank the gods for the confusing world of computers!
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!