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I am trying to connect multiple peripherals to my laptop, and I want to be sure that I have enough support for all of them.

The power was my main concern, but then I realized that maybe even attaching devices that are self-powered, I could still get in trouble with enumeration of the USB ports if I have too many devices.

At the moment I have the following devices:

  • Oculus rift with 3 cameras (4 USB ports and 1 HDMI, USB-powered)
  • Steinberg Ur22 (self powered 1 USB port)
  • Logitech wireless receiver for KB and mouse (1 USB port, USB-powered)
  • Wireless adapter for Xbox360 controller (1 USB port, USB-powered)
  • 3d mouse (1 USB port, USB-powered)
  • Gaming keypad (1 USB port, USB-powered)
  • HOTAS (1 USB port, USB-powered)
  • Racing wheel with shifter (2 USB ports, one self-powered the other USB-powered)

My laptop has 4 USB 3.0 connections, I have connected a powered 4-port hub and a non-powered 4-port hub; so I have 10 available ports.

I do not connect all the peripherals at the same time, but I have some that are always on, like the audio mixer, the keyboard/mouse receiver, the 3D mouse, and the gaming keypad, which fill 4 of the available ports already.

I also have the cameras for the Rift always connected. So I usually have only 2 ports free to swap.

If I connect another two powered USB hubs, would I be able to plug all the devices permanently, and not overload the system, or is there a USB limit that would require connecting-disconnecting peripherals based on usage?

From what I recall, USB supports 127 devices chained, but my experience has been otherwise. Both my previous desktop and my current laptop, at times, just lose devices when too many are plugged in. I think the most I can connect before degrading performance is 8.

Also, might it be less problematic to have one bigger USB hub (like 8 ports), instead two with 4 ports? I am not sure whether I can use full power on all ports at the same time due to hardware limitations.

  • 2
    This is not a shopping question. The question raises a concern that if there are "too many devices" (but still much less than 127 per root controller), there is some limit, all based on anecdotal evidence. The premise of the question is wrong: there is no "power limitations" with self-powered hub, other than if they are sloppy engineered, and are not properly protected from inrush currents and droop cross-talks, or devices are used which are not compliant to USB specification (in terms of initial max load capacitance). – Ale..chenski Mar 26 '18 at 5:36
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    If you use USB-IF certified components, there is no "hardware limitations", other than maybe bandwidth allocation restrictions on high-bandwidth devices as lots of 4K HD cameras. But might be a challenge to find a good USB-IF certified hub these days. – Ale..chenski Mar 26 '18 at 5:41
  • Thanks for the replies. Indeed I have no idea about the real scenario VS the on-paper scenario (127 chained devices). From what I read, I should have no problems, but in facts, I see that the devices conflicts with each other, and I have no way to know if the quality of the USB controller on the motherboard is good or not. Regarding USB-IF, are they marked as such or is something that can be "faked"? The powered hubs I did find, do not carry much info beside "3.0, X ports, Y watts of power for the AC adapter". – rataplan Mar 26 '18 at 6:51
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    Queries such as, "IF I get another 2 powered USB hub?"..."would [it] be worth [it] to get one bigger USB hub?" fall in the domain of making a shopping request. You're asking for information upon which you would base a purchase decision. If you meant to ask for a solution to a problem, state what the problem is and ask how to solve it. – Twisty Impersonator Mar 26 '18 at 14:50
  • The solution to your question is "Have you tried it yet". If your answer is "no", the follow-up question is "why not, because that would answer your question". None of your described circumstances come close to the limits I am aware constraining USB connections. – music2myear Mar 26 '18 at 19:20
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The power was my main concern, but then I realized that maybe even attaching devices that are self-powered, I could still get in trouble with enumeration of the USB ports if I have too many devices.

You are not close to the USB limits in terms of device count or power (assuming you have compliant devices and they're connected to appropriate ports).

Both my previous desktop and my current laptop, at times, just lose devices when too many are plugged in. I think the most I can connect before degrading performance is 8.

You should be able to use all of the ports on any hub simultaneously if you are not exceeding its power limits.

A non-powered hub has to supply power to all of its ports with what is left over after powering itself from the power it receives via its single USB connection to the computer. So all of the connected devices need to be low-power-demand devices.

Self-powered devices get a low-current USB connection, so they should not put high power demands on a port. They're good devices to connect to a non-powered hub. You might want to verify that their power adapters are not defective (e.g., does the device work, or at least indicate that it has power, when it is not connected to the USB port).

Not all devices are well-behaved, so if you are having problems with low-power devices on a non-powered hub, try replacing it with a powered hub.

A powered hub should be supplied with enough power from its own power adapter to provide full USB power to all of its ports simultaneously. As long as none of the attached devices try to draw more power than the USB limit (which would make it a non-conforming device or defective), power should not be a problem. However, check the rating on the hub's power adapter to verify that it is sufficient to power all of the ports (we recently had a question about a powered hub and the hub's power supply was inadequate).

I'm not familiar with the data levels of all of your devices. All of the data for all of the devices on a hub has to be funneled through the single connection between the hub and the computer. If you exceed the bandwidth of the hub's computer connection, you could see some performance degradation, but that would not manifest as losing devices.

The symptoms you describe of losing devices sounds like either a power issue or defective hub or port if it isn't due to a defective or malfunctioning device (if it's always the same device that gets lost, especially if that is regardless of where it is connected, suspect the device).

If I connect another two powered USB hubs, would I be able to plug all the devices permanently, and not overload the system, or is there a USB limit that would require connecting-disconnecting peripherals based on usage?

You can connect as many hubs as you want to the computer's ports, even connect hubs to those hubs. Each USB bus allows a maximum of 127 devices, and each hub counts as a device against that limit. You can connect a chain up to five tiers of hubs. You will want to use powered hubs if you daisy chain them.

USB hubs in general have a reputation for being crappy hardware with high failure rates. If you are using USB hubs and have problems with devices connected to a hub that you shouldn't have because you aren't violating any USB limits, the hub is one of the first things I would check.

To summarize things to check:

  • Verify that the only devices connected to a non-powered hub are self-powered or low-power devices. Consider replacing the non-powered hub with a powered one.
  • Verify that the power adapters are functioning on self-powered devices.
  • Powered hubs sometimes have a switch to set whether they will be operated as powered or non-powered. Verify that the switch is set to powered if there is one.
  • Check the rating on the hub's power adapter to verify that it is sufficient to power all of its ports.
  • If the same device is lost repeatedly, try connecting it to another port, especially on another group of ports. For example, if it loses its connection on a hub, try connecting it directly to one of the computer's ports. If the device acts up regardless of where it's connected, suspect the device. You could try it on another computer to see if it fails there, also.
  • If the problems are with multiple devices on the same hub, try connecting the hub to another port on the laptop, especially one in another location on the laptop if there is one. If it's problematic there, also, try another USB hub.

Those are all simple things to check to rule out the common causes. If none of those solves the problem, update your question with the details and we can try a bigger hammer.

  • Thanks a lot for the info! I will give a try with a different powered usb hub and see if that will solve the problem (which in that case would be due to the excessive voltage used by my peripherals on the same port. By the way, is there a way to know how much current a device use? I did check the tech specs for some of them but I see nowhere the actual power; and for the powered ones, I can read the voltage of the AC adapter, but that does not necessarily mean that the device is using all the power. Thanks! – rataplan Mar 27 '18 at 2:53
  • @rataplan, the current usage is actually a little complicated. Explaining it wouldn't fit in a comment and it's kind of tangential to this already long answer. If you ask a new question specifically about that, we can give you a dedicated answer, which would also be easier for other readers to find. – fixer1234 Mar 27 '18 at 3:13
  • @fixer1234, USB system can have no more than 5 hubs in a chain, not seven. Please correct the answer. – Ale..chenski Mar 28 '18 at 7:39
  • +1 for crappy hubs. Most frequent problem with hubs (most of which are crappy in terms of power distribution) is that the inrush currents (plug-in of new devices) create voltage interference with adjacent (and active) ports. It is called "droop". You need a special test fixture to check for droop compliance. Or a new device inrush might create a glitch on upstream data creating a condition known as "babbling device", which forces the host to disconnect the entire hub and re-enumerate the corresponding branch anew. Detailed observation on when the disconnect happens would help to diagnose. – Ale..chenski Mar 28 '18 at 7:50
  • @AliChen, 5 hubs rang a bell, but I wanted to double check it, and that's where the 7 came from. I didn't have ready access to the spec, and misread the source I checked. I had written 7 including the internal root hub. It's 7 tiers total. If the last tier was a hub, you couldn't connect anything to it. So, yeah, 5 external hubs max. I clarified the wording. Thanks. – fixer1234 Mar 28 '18 at 10:10

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