Talk:USB hub

What's up with the patent citation?
This article contains a very specific citation to a single US patent; something I don't usually see on Wikipedia. Perhaps this should be trimmed somewhat? Sim (talk) 22:30, 29 April 2010 (UTC)

usb hub powered by batteries
Does anyone make a battery powered usb hub, that will allow you to use a usb host that doesn't have power to talk to devices that are not self powered? Basically I'm asking for a battery self powered usb hub. —Preceding unsigned comment added by 66.202.48.225 (talk • contribs)
 * dunno if anyone makes one as a single unit but you could always look at the power requirements of a USB hub that takes DC power and build a battery pack to go with it. Plugwash 23:36, 1 November 2005 (UTC)

The CyberPower CP-H420MP is a battery powered 4-Port USB Hub: http://www.cyberpowersystems.com/CPH420MP.asp pdecat

usb 2.0 hubs
can a hub that doesn't support high-speed mode be compliant with the usb 2.0 specification? Plugwash 00:37, 3 January 2006 (UTC)
 * yes, because the 2.0 specification is backwards compatible with previous specifications therefore a full-speed (1.1 compliant) hub is compliant with the 2.0 spec. You could theoretically build a full-speed hub with a tt in it, but I don't know there would be a point to doing so. SchmuckyTheCat 08:25, 3 January 2006 (UTC)

Maximum number of downstream ports, on a self-powered hub
What is the maximum number of Downstream ports, one can possibly implement on a self-powered USB hub device? (not using host supplied power) I've seen 4 & 7 ports hubs maximum, all which are bus-powered. Is there any place that can say for sure? I tried browsing the USB 2.0 Spec, but can't find the definition - unlimited, or if limited what is the limit? Maybe 8, since Port 0 would be the upstream port, which leaves 1-7 for downstreams.

~Robin
 * I removed your email address so that it does not get spam harvested.
 * The answer is "as many as you can power". You've got 500ma of power from the bus, the hub itself uses some. From there you can have as many devices as you can power up. Some HID devices use as little as 25ma.  An important consideration is that many bus-powered hubs don't report correctly as bus powered.  They report self-powered to the controller. Because of this, you can often plug a bus-powered hub into another bus-powered hub. This breaks the spec but if you really wanted to play a game of "how many bus powered devices can I have off one bus powered port" it allows more. SchmuckyTheCat 16:22, 30 July 2006 (UTC)
 * Afaict from a compliant equipment point of view you are limited to 4 as usb allocates power in units of 100ma (so thats one unit for each downstream device and one for powering the hub). There isn't anything to stop hub vendors breaking the spec though. Plugwash 17:37, 30 July 2006 (UTC)

It seems like that maximum would be about 127 ports on a hub, based on the good main USB article. As a practical matter, it seems like you would assemble a large tree of 7-port hubs. Eight of them would be a full two levels, and offer 49 usable ports -- and a total of 24.5 amps if everything was working right. 69.87.200.138 22:55, 6 December 2006 (UTC)

My reading of the USB 2.0 spec is that upto 255 ports are allowed on a hub (see section 11.23.2.1 description of DeviceRemovable field). This isn't very useful of course because only each host can only address 127 active addresses so building a hub with more than 126 addresses (one for the hub) won't be very useful. —Preceding unsigned comment added by 212.159.70.1 (talk) 11:27, 26 October 2008 (UTC)

what can be connected to a hub
Are there any guidelines as to which devices you can connect using a USB hub? I have a laptop with only two USB ports. I have a printer, mouse and cell phone and am thinking about connecting an external hard drive as well. It is my understanding that some devices have to be connected directly to the port and won't work when connected to a hub. Rebel69 13:41, 15 August 2006 (UTC)
 * Its pretty much a case of suck it and see, there are three issues to be considered. Firstly the power issues mentioned above (the devices connected downstream of a compliant bus powered hub can only draw a total of 4 100ma units of power, a noncompliant bus powered hub may allow more and a self powered hub should only be limited by the hubs power supply system). Then there is the issue of buggy drivers (e.g. when i plugged my mplab ICD2 into my belkin USB2 hub and installed the drivers it bluescreened windows). Finally there is the issue of bus bandwidth, especially if the designers weren't carefully about transfer modes (this can also happen without a hub depending on the systems usb controller design). Plugwash 16:08, 15 August 2006 (UTC)

internal (PCI) vs. external USB Hub
Which USB Hub is recommended for a PC (Desktop, Windos XP) external or internal ? Thank you! chtzou 19:58, 18 August 2006 (UTC)


 * If its actually connected to the PC via PCI then its not a hub its a seperate USB controller. A seperate controller will give better performance than a hub if you have lots of high bandwidth devices and may also be usefull if you have devices that don't get on with hubs otherwise its a waste of money.


 * If its just drawing its power from the PCI slot and connected to the PC via usb then it will perform just the same as a self powered external hub. Plugwash 23:45, 18 August 2006 (UTC)
 * Do such actually exist? 69.87.200.138 22:58, 6 December 2006 (UTC)
 * Dunno, I've never seen one but there is no reason it couldn't be made. Plugwash 13:00, 7 December 2006 (UTC)

"Common knowledge" is not the same as "original research"
I took the Original Research tag off of the paragraph about noncompliance. For devices that don't announce themselves, see any of the USB-powered lights/lighters/vacuum cleaners. They just yoink the 5V power, without connecting anything to the signal pins. Most powered hubs are non-compliant. Even a high-end hub like the DUB-H7 has 7 ports, advertised at 500mA each (for 3.5A), but only a 3A power brick (and part of that power goes into powering the hub and losses too). By the specs given on DLink's web site, it simply cannot supply the claimed 3.5A. That's still one of the better ones. See reviews on newegg.com with people not being able to use USB drives with many so-called powered hubs. Hell. I've designed plenty of non-compliant devices myself. Of the cheap devices I've bought, I would guess the majority were non-compliant (this doesn't extend to fancy expensive things).

Cites are good, but not necessary if something is commonly known. —Preceding unsigned comment added by 68.160.158.59 (talk • contribs) 31 December 2007
 * Please do not assume that random information is common knowledge. This certainly doesn't qualify. Chris Cunningham 01:54, 31 January 2007 (UTC)

"Length limitations"
I think it would be helpful to list the length limitation in greater detail. See "Cables and long-haul solutions" at http://www.usb.org/developers/usbfaq/

It might also be worth mentioning the maximum of 5 daisy-chained hubs between a device and the host computer.

Technical limitation
I reverted the addition of this section. It stated that you can't have two usb-storage devices attached to the same hub (only one works). I just tried that with 2 pendrives, and both worked fine. Tizio 13:13, 5 September 2008 (UTC)
 * Absolutely. I have a 500Gb USB HDD and also plug my thumb drives in on the same hub. Never had any problem. There may be situations where it may cause problems, but I haven't experienced any. 'Non-compliant' devices may be troublesome perhaps? --220.101.28.25 (talk) 01:56, 1 November 2009 (UTC)
 * Based on past experience, the issue may arise if one of the devices isn't USB2.0 compliant, or if the hub itself isn't USB2.0 capable. Anecdotally, I've had an eight-port hub with two thumb drives and a 160GB portable drive all connected at the same time, and both WinXP and Linux had no problems differentiating or accessing the devices. All were USB2.0-compliant. Alan (talk) 02:10, 1 November 2009 (UTC)
 * This is why OR is a problem. The guy may have had a 'bad' port, 'bad' thumb drive. The entry was very poor English as well!.--220.101.28.25 (talk) 02:36, 1 November 2009 (UTC)
 * There are lots of devices out there that play fast and loose with the USB specs. For example bus powered hubs that claim to be self powered hubs, devices that don't correctly declare their power use, devices that draw more than 500ma and devices that can't work over the full range of allowed USB voltages. So rather than error messages about insufficient power you get flaky behaviour as the voltage drops below what the devices needs. Plugwash (talk) 13:31, 11 January 2012 (UTC)

Mixed speed devices
I have seen it suggested that if USB 2 and USB 1.1 devices are connected to the same USB 2 hub all will work at USB 1.1 speed. I don't know whether this is true always, under some circumstances or never but it would be good to see this clarified in the article. treesmill (talk) 23:01, 23 May 2011 (UTC)
 * Don't use cheap crap. No compliant hub does this. It is explained in the speed section. SchmuckyTheCat (talk)

Is a 16 port hub really a chain of FOUR four port hubs?
I think the 'Electronic Design' section needs looking at

wouldn't you need five four-port-hubs to make one 16-port-hub?

that's four hubs for the sixteen possible connections and another to connect all of them to one connection.

or if they are in a chain you would have each with three available and one used for the next hub (until you get to the last hub which has all 4 available) 3 + 3 + 3 + 3 + 4 = 16

Danieljabailey (talk) 09:56, 3 January 2013 (UTC)
 * Hope this is more accurate. AgadaUrbanit (talk) 10:13, 3 January 2013 (UTC)

USB 3.0
The discussion of hubs mentions only USB 1.1 and 2.0. USB 3.0 ports and devices (including hubs) are now widely available. It would be very useful for the article to include 3.0 hubs as well (if only to say whether the information does or does not apply to 3.00 devices72.93.83.215 (talk) 14:28, 23 April 2013 (UTC)Nick Nichols

invalid url: domain name up for sale.
http://www.hkcolordigital.com/industrial-usb-16-port-hub.html — Preceding unsigned comment added by 117.254.220.104 (talk) 16:10, 23 May 2014 (UTC)

What is between 1.1 and 2.0?
"Any USB 2.0 hub that supports a higher standard than USB 1.1 (12 Mbit/s)" — Preceding unsigned comment added by ShalokShalom (talk • contribs) 10:05, 14 December 2016 (UTC)

Transaction Translator and USB 3
The article as currently written states that there is not currently not a Transaction Translator between USB 3 and USB 2. While technically correct, there would be no point to having such a thing. Because the USB signals use a completely separate set of wires, so that USB 2 signals cannot slow USB 3 transactions. Indeed, the case is the other way round: USB 2 and 3 wires can be used at the same time to different devices, and translating USB 2 onto USB 3 would actually slow the system down. The statement should be removed. Whether there should be a statement about the lack of need is a matter for discussion.

Alec (talk) 22:12, 28 April 2020 (UTC)

Source for 16 Port USB Hubs
I've found this https://www.sabrent.com/product/HB-PU16/usb-3-0-16-port-aluminum-hub-with-power-switches-and-leds/ link, selling a 16 port USB Hub. Would this be a reliable source for https://en.wikipedia.org/wiki/USB_hub#Electronic_design ? LewisSpring (talk) 15:49, 11 May 2021 (UTC)
 * , We don't use vendor marketing materials like that as sources. MrOllie (talk) 15:57, 11 May 2021 (UTC)
 * I didn't think so. Thanks :-) LewisSpring (talk) 15:58, 11 May 2021 (UTC)