Talk:USB/Archive 1

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Archive 1 Archive 2 Archive 3 Archive 5

Embedded HCDs

Q: Obviously HCD implementations both hardware and software are complex and I assume difficult to implement. That’s why they reside in the PC.

However I wish to develop an embedded HCD for an industrial application. Can you suggest a suitable microcontroller implementation.

It depends on what you wan't out of it, if you know you will only even be connected to one low speed device with no hubs then i belive it can just about be bit banged on some of the faster 8 bit microcontrollers (i belive the particular device in this case was a ubicom sx). If you wan't full speed you are into the realm of chips specifically designed to be usb hosts, how much power you need depends on the application.
If you wan't a fully generalized host interface your going to be into the very high end of the embedded processor market (e.g. generally things that use seperate ram). Depending on the budget/volume you might wan't to consider an off the shelf soloution like the linksys NSLU2 (they sell it as a storage server but its linux based and can be loaded up with whatever apps you need memory and CPU speed permitting). Plugwash 17:27, 15 September 2006 (UTC)

Use of SCSI Command Set by USB

Q: I think it would be useful to mention that USB uses the SCSI command set, despite adopting a different physical architecture. This is actually highlighted in the SCSI article. As the current article stands SCSI and USB seem like completely unrelated technologies. Nick 08:50, 20 Aug 2004 (UTC)

A: See USB Mass Storage Rationale of SCSI over USB.

Please specify USB version

"USB has a Full Speed rate of 12 Mbit per second." Is this version 1.0 or 1.1?

no one knows. - Omegatron 14:36, Jan 15, 2005 (UTC)
  • ? whaddya mean nobody knows? VERSION NUMBERS MEAN NOTHING TO THE SPEED. DO NOT PAY ATTENTION TO VERSION NUMBERS. Full speed is 12Mb. Always, has been, since .9 at least. SchmuckyTheCat 19:25, 15 Jan 2005 (UTC)
  • update to myself, Full Speed has always been in the spec, with bandwidth testing of multiple FS devices being included as reference at 0.9 SchmuckyTheCat 17:11, 8 Mar 2005 (UTC)

Can someone please explain usb cable types

I know there are at least two and maybe more types of cables for USB - Could someone differentiate them? Is one type of plug/cable for USB 1 and another for USB 2? Or does the cable/plug type not matter? I know they are compatible, does one cable/plug limit the bandwidth?

I have tried to find this on the internet but my searches only turn up vendors trying to sell stuff - it is overwhelming.

Could someone please research this and maybe even put pictures of the USB plug types up on the page?

Oh, and I know that a USB 1 hub would have to be replaced to handle the bandwidth of USB 2, but I do not know if the cables make a difference.

While Richard's answer (below) is true it is slightly unclear. These are some difficult questions. The facts in my post are based on information made available by the USB Implementers Forum, including the USB 2.0 spec.
First you should know that captive cable means a cable where the device end is either permanently attached to the device, or is detachable, but uses a connector other than the ones specified by the usb standard.
Also note that usb cables cannot contain usb ports. (USB extention cables are not permitted by the USB Spec).
The legal cables are:
  • A to B
  • A to mini-b
  • A to captive
  • mini-A to mini-b
  • mini-A to captive
There is also one legal adapter which consists of a USB A connector and a usb mini-A socket. (This is the only legal use of a mini-a socket.)
The usb 1.0 cables will probably work with high-speed usb 2.0 devices, but it is possible that problems may occur. If a cable claims USB 2.0 support it should work for all devices.

The link to the USB.ORG site includes access to the specs for cables which include pictures (drawings). The A end hooks to the host and the B end hooks to the device. As noted above, in the extension called On-the-go, there is also a hermaphroditic socket which will accept either the A or the B end of the mini-version of the standard cables.

There is no plug/socket change for High speed (480Mpbs) but the cable spec was tightened in the 2.0 version to allow for the higher transfer rates. A 1.1 Spec. hub will work on a 2.0 system but will limit the maximum speed of any down-stream devices to 12Mbps regardless of whether the downstream devices are High-speed capable or not. - richard

USB A-A cables

Can someone write in detail on the topic of USB A-A cables? From what I know, there are 2 types of these:

  • Plain A-A cablle
  • A-A with electronics

I don't know what the first one is used for, it costs ~$5 (nominal cost - cable and 2 terminals). The latter can be used to connect 2 computers and includes some kind of device, so that files can be copied (~$50). I have some info that files cannot be copied from computer to computer on the plain ones because USB is an asynchronous protocol, but I don't understrand the technical details. Any info on this? Any software workarounds for file transfers using the cheap cables possible?

Helix84 13:25, 3 Nov 2004 (UTC)

There shouldn't be any topic of USB A-A cables. The ones that have electronics in the middle are just another device. The electronics just expose a bulk interface on each side, one to each host controller. These usually require some special software that sends files or whatever over the bulk interface to the same software running on the other machine. These aren't deserving of their own topic, they're just another device.

Those that don't have electronics in the middle are invalid according to the spec. Since the first machine you plug one into is sending 5v and the next machine you plug it into EXPECTS to send 5v, you're just likely to blow the motherboard of one or both machines. Just bad, bad, bad. Of course you occasionally run into some no-name stupid device that uses an A-A as a device cable, avoid them like the plague. If they couldn't even get the cable spec right it's unlikely the device will work well AT ALL. -- SchmuckyTheCat 8 Dec 2004

At some point I was going to add a section on those little USB PC-to-PC networky things (but I confess I've never used one, never seen one, and I'm really not sure what they're officially called). That section would have a one-liner explaining why an A-A cable wouldn't work. I suspect that in addition to the "you cooked my motherboard" phenomenon, there's the unavoidable fact that the low-layer protocol handlers (built into the relevant host controllers) aren't built this way (unlike those in USB-to-go) and anyway the resistors that balance the datapair will be doubled (which isn't good). - John Fader 03:31, 9 Dec 2004 (UTC)
we bought a bunch of one brand and reverse engineered our own driver for a few purposes: throughput, loopback, and bit verification testing. yeah, it might be worth a few sentences of "dispelling common misperception" in the discussion of cable types.

- SchmuckyTheCat 22:42, 8 Dec 2004

Another possible reason for wanting an A-A cable is an A socket looks a lot easier to breadboard with than a B Plugwash 14:45, 9 February 2006 (UTC)

Gender Changers

The claim is made that "Unlike other communications systems (e.g. RJ-45 cabling) gender-changers are never used, making it difficult to create a cyclic USB network.". However gender changers do exist. See, for example,

I suggest changing "never" to "rarely" or "usually not".

No, they are never used. A true gender changer (with no active circuits, unlike some adapters which look like gender changers but are in fact two separate USB devices) will not work. The whole signalling protocol USB uses depends on its tree topology. --cesarb 16:09, 26 February 2006 (UTC)
but surely you could have a working system with a gender changer and an equally dodgy A-A cable ;). Seriously someone must wan't this shit or noone would make it. Plugwash 00:07, 27 February 2006 (UTC)
What qualifies as a "gender changer"? I actively use a female A to female A changer (much like the ones here) to convert a male Mistumi Mini-B to male A cable so as to accept a male-A device. I suppose I should take the spare apart to see if there's circuitry crammed inside. - Keith D. Tyler (AMA) 17:32, 27 July 2006 (UTC)
Many people in RS-232 speak of gender changers that are actively x-over (null modem). Such a cable shouldn't exist in USB. The little coupler dongles are wired straight no matter which end (a, b, mini) is plugged into each side. SchmuckyTheCat 20:07, 27 July 2006 (UTC)

USB 2 HS vs. FireWire

I would like to comment on USB2.0 being in direct competition with IEEE 1394. Here are a list of features that makes then resolutely different:

Application domain

  • USB addresses needs for a wide range of devices (mouse, keyboard, modem, hard disk drives, scanner, printer...) that do not exist in IEEE 1394.
  • IEEE 1394 addresses needs of audio-video devices such as videorecorder, digital camera that have no real equivalent on USB.

USB's isochronous mode does apply to streaming devices including videorecorders and audio devices such as speakers, microphones, etc. The High-speed (480Mbps) use of isochronous is directly comparable to use of IEEE 1394/Firewire for these devices - richard

Communication paradigm

  • USB provides host to peripheral communication. A host computer is required in the system.
  • IEEE 1394 provides non-centralized networking. You may build a network with simply a VCR and a TV tuner.


Yes, the system requres a host - but the USB On-the-go extension allows for the possibility of a unit that is usually used as a device to become a host for the purposes of a point to point conversation as you describe. The initial setup is determined by which end of the cable is plugged in to which unit but is switchable under software control so that the initial device may assume host and vice versa. The USB OTG sockets are hermaphroditic - can accept either the A or B end of the cable. - richard

USB OTG still does not provide true MULTIPLE peer-to-peer communications. In all instances, there MUST be a host, even if you can switch between them. USB OTG doesn't allow for a drive enumerate other devices if it is not the host, so a non-host OTG device (B) that wants to talk directly to a third OTG device (C) can't do so without re-arbitrating the bus and potentially screwing up any communication the host (A) was doing with device B or C. Plain and simple, OTG does not suddenly give USB feature parity with FireWire.

Firewire/USB 2 HS Mix up?

In the section comparing USB to Firewire, it states that Firewire's preformance degrades as the number of devices increases. However, it has always been my belief (and to many sources I have seen) that the architecture of firewire allows for multiple devices without much loss in speed. It is the USB architecture that suffers from this flaw. -Nick2253


"USB 2.0 boasts 480Mbps throughput"

I don't think so. USB 2.0 does signaling on the wire at 480 megacycles per second. The physical layer transports up to 480 million bits in one second. But that doesn't mean it has 480 Mbps throughput. In fact, it pretty much guarantees the throughput is less than that.

Looking at the spec, the fastest way to transfer data seems to be with a high-speed bulk transaction with a data payload of 512. This gets you (see p.55) 53248000 bytes/second of bandwidth, or just under 426 Mbps throughput. And that's assuming you can saturate the line with 100% high-speed bulk transactions; I think you have to have other transactions going on to request all that data, which is why even the theoretical throughput is lower than 426 Mbps.

Am I missing something?

I haven't seen the Firewire spec, but it probably has something similar going on. I doubt it has 400 Mbps of throughput. But it does seem to perform better than USB 2.0: this should be a good indicator that USB doesn't really "boast" more "throughput".

FireWire of course doesn't have 400Mbps throughput, but it has a much more efficient signalling system (clock & data separate in 1394a, 8b/10b-style full duplex in 1394b). Also multiple devices can communicate simultaneously, while USB is basically a broadcaster-listener system so that all packets occupy all the bandwidth all the time. Also the FireWire system allows for extremely low DMA overhead, while USB requires a great deal more marshalling, decoding, blah blah. By my reckoning, you're lucky to get even 40-50% efficiency at either full-speed or hi-speed with USB, because of the signalling method and tremendous overhead, and the measurements I've seen support this --- Mpa 07:47, 30 December 2005 (UTC)

In practice, and I believe that anyone with substantial experience with the two technologies will agree, FireWire has better throughput. Period. What is stated in the article about USB having better throughput is just plain incorrect.

USB 1.0, 1.1, 2.0

"Confusingly, the USB Forum has renamed USB 1.1 to USB 2.0 Full Speed; and USB 2.0 to USB 2.0 High Speed."

Are those definitely absolutely the same? Please provide a reference. I find conflicting info online. - Omegatron 22:39, Nov 6, 2004 (UTC)

subsequent edits deleted that info, it was wrong. - ???

I was looking into this topic recently and found a bit of info, nothing definitive though, and the site 1) is not the easiest to navigate and 2) removes old info.

Seems this event happened sometime in 2003.

  • an site article
  • it's source (does not exist on www or in wayback machine, so google for other sites using it)

- Brewthatistrue

Maximum cable length

I think about adding a mention of maximum cable length, for people (as I was) concerned about the distance between two equipments. There's an answer on the USB Info: Frequently Asked Questions. Any comment ? - --Olivier Debre 09:02, 18 Jan 2005 (UTC)

Certainly this should be included. Explain why cable length matters and explain the changes in recommendations by the (Originally it was a length, but they changed it to a signal integrity spec instead.) - Omegatron 21:49, Jan 26, 2005 (UTC)
Definitely. The information is readily available. I apologize for not taking the time now to do the work. The use of hubs and other techniques to extend length should also be mentioned. Joaquin Miller 16:29, 4 September 2006 (UTC)

interrupts and synchronization

Which way are frames initiated? Does the host/hub send out a frame to each device every ms, or do the devices send out frames every ms? Since the clocks of the devices would vary slightly I would imagine the host does. How does the USB host interrupt the CPU? Where can I find more details about these, since they may be too technical for this article? - Omegatron 21:47, Jan 26, 2005 (UTC)

  • the USB host sits on an internal bus in the PC. HCD --> bus --> CPU I don't know of any implementation of USB that isn't PCI, but maybe Mac's or other non-x86 architectures use some other internal bus, I've never had to care. On Windows the USB stack transfers URB messages between driver components, URBs are equivalent to IRPs in the rest of the Windows kernel messagaging interface. SchmuckyTheCat 03:58, 31 Jan 2005 (UTC)
 :-) Well, at least I know of some acronyms to look up now... - Omegatron 04:06, Jan 31, 2005 (UTC)
Host controller device (USB host), Interrupt return pointer, USB Request Block - Omegatron 04:11, Jan 31, 2005 (UTC)
  • also, i gave you an incomplete answer. the bus has 10% of the traffic reserved for control purposes - so devices DO keep in synch. it also uses control to make sure everybody gets a chance to talk, but who talks is dependent on the type of traffic they want to send (see the transfer types under technical details). transfer types have priority: control, interrupt, isoch, bulk. interrupt devices can interrupt but they don't send large amounts of data, so this shouldn't interfere. isoch devices reserve bandwidth in an OS dependent fashion (on windows it's first-come first-served and no hoarding) so they can talk as much as they want in their reserved pipe. bulk devices talk when the HCD tells them too and they get whatever bandwidth is left over. they have to scale back when something else is going on. simple enough. but then: see also how the virtual 1.1 HCDs in EHCI create virtual busses on the same wire, and how the TT virtualizes 1.1 traffic in a 2.0 hub. i think i'll do a re-write of portions of the article for this, the article is currently too technical for simple concepts to come out of it.
I don't really understand all of that. One thing I was asking was, since the host and devices each have their own clocks, which clock is used to synchronize transfers between them? I assume the host clock, and the devices only send data when they are spoken to? - Omegatron 18:42, Jun 6, 2005 (UTC)

Types of USB connectors

Would anybody who knows this topic well care to add pictures and information about the various types of USB connectors, such as Type A, Type B, and mini USB? — Brim 08:28, Feb 5, 2005 (UTC)

- Brewthatistrue 16:29, 26 August 2005 (UTC)

I agree. A side-by-side comparison of the types of connectors would be incredibly useful, especially considering that an increasing number of digital cameras and mobile phones are using mini USB connectors that most people may not find familiar. Here's a link with side-by-side images of female and male mini connectors:

Which information should be hidden or removed?

I simply wanted to add information that some people might want to know: USB 1.1 introduced Full Speed, or 12.5 Mbit/s transfer speed. In my first edit, the wording was poor but not factually incorrect when I said 1.1 had Full Speed. Then an unnamed editor reverted it, stating that version 2.0 also has support for Full Speed, not just 1.1. Not a valid argument at all for a revert, but a true statement nonetheless, I thought, so I simply added more information to this for clarity and said 1.1 introduced Full Speed. This was yet again reverted by the same editor. It seems like this person has an agenda of removing information from the main article. Strange, since one would think an Encyclopedia would be a place where you add, as opposed to remove, information (especially the ones people would likely to be interested in). As a consumer, I would like to know as a basic fact what speeds are associated with the version number of a USB port. SchmuckyTheCat thinks otherwise, and believes that this information must be hidden from plain view. At his/her request, I have created a section where s/he could respond, hopefully without the caps-lock on. -- 20:19, 8 Mar 2005 (UTC)

First off, please don't make a technical discussion into a personal conflict by making comments about other users and what you imagine their motives to be. Let's just stick to the article, okay. Now, it's clear that there's disagreement both about what speeds were introduced when, and how we should present this. I think we should have a "feature table" showing the different versions of USB, their features, and significant changes. Now, as to which version did what: sources need to be cited, particularly so now that there is controversy. A source in this case is ideally the version, page, and line number (and ideally a quote) from the official USB spec. When this (surely an unimpeachable) source is available, bickering without citing exact references is a waste of everyone's time. -- John Fader (talk · contribs) 20:50, 8 Mar 2005 (UTC)
This info was wrong in the past and someone fixed it. See above. Please don't change it unless you know for certain you are right. Cite your sources to prove it. - Omegatron 22:38, Mar 8, 2005 (UTC)
  • Full speed has always been part of the spec, probably since the version number was just an idea in a few engineers head. It was never introduced, it has always been. I'm actually interested to see why you think this is true. Is there another website or product literature saying this? I understand the user confusion, but the version number of a port doesn't correspond to speed. Like all technical interfaces, the new interface is "faster, better, cheaper" than the last but backwards compatible. You never, for instance, talk about RAM as being DDR v2.0. It's DDR266 or PC2100, and of course the faster stuff slows down in a slower slot. Unfortunately, some USB device marketers started advertising the version number as a speed indicator, which is enitrely misleading. A USB 2.0 device might only do Full Speed (12mb). What sells more, a 12mb device that says "12mb" or a 12mb device that says "USB 2.0"? A device might even do 480Mb, but the manufacturer fails to get it certified (maybe it fails other parts of the spec). They can't put the Hi-Speed logo on the box, but they can say 2.0. "Hi-Speed" is trademarked. "2.0" is not. A smart consumer should look for certification logos and declared speeds, not version numbers. SchmuckyTheCat 15:16, 9 Mar 2005 (UTC)
  • Also, see previous discussions on this on this talk page under "Please specify version number" and "USB 1.0, 1.1, 2.0" SchmuckyTheCat 18:07, 9 Mar 2005 (UTC)

What is the difference between USB 1.0 and 1.1? If they supported the same device speeds, someone had better go tell list of device bandwidths, which may or may not be confusing Low-Speed/Full-Speed with 1.0/1.1. (It lists 1.1 as being faster than 1.0; can someone who knows the difference go look?) What benefits did moving to 1.1 offer for devices that made up for breaking compatibility with 1.0 host controllers? grendel|khan 19:05, 2005 Mar 9 (UTC)

  • krikey, what a mess that list is. I will go correct. If someone writes a USB history section the difference between 1.0 and 1.1 would be: pretty much nothing. SchmuckyTheCat 19:44, 9 Mar 2005 (UTC)
  • USB 1.0 was both 1.5 and 12Mb/s, supported only Isochronous and what was called Asynchronous at the time ('96 Winhec notes) 01:33, 13 December 2005 (UTC)


cable has a characteristic impedance of 90 ohms. each driver should be 45 ohms ± 10%. for high-speed, each receiver shuold also be 45 ohms, standard nonreflective impedance matching. not sure if the 45 ohms are required for low/full speed devices though. - Omegatron 20:22, Jun 6, 2005 (UTC)

Actually it's more complicated than that:

"When the full-speed driver is not part of a high-speed capable transceiver, the impedance of each of the drivers (ZDRV) must be between 28 Ω and 44 Ω, i.e., within the gray area in Figure 7-4. When the full-speed driver is part of a high-speed capable transceiver, the impedance of each of the drivers (ZHSDRV) must be between 40.5 Ω and 49.5 Ω, i.e., within the gray area in Figure 7-5." - Omegatron 20:36, Jun 6, 2005 (UTC)

TCP over USB?

Is it possible to do a TCP type network over USB? I know FireWire is cappable of such a feat, but I was wondering if the 2.0 spec of USB have such a feature. If so, would it then be possible to network a USB printer or cammera remotely? I don't really care about IP, but I'll still take the information if anyone knows. Thanks guys! CoolFox 03:41, Jun 24, 2005 (UTC)

No, not really. Not saying it's impossible, but on devices there isn't a native, or even proposed native, or even an OEM implementation, that I am aware of. IP over 1394 has interoperability of implementations approaching zero, remoting of 1394 devices is nearly always done through a host PC. Remote cameras, printers, and storage are all universally ethernet (that includes wi-fi) devices. SchmuckyTheCat 14:07, 24 Jun 2005 (UTC)
Are you thinking of something like USB On-The-Go? That would allow, for instance, your camera to talk to your printer, though both would have to be USB OTG supporting devices. I'm not sure what your goal is---can you state what it is you'd like to be able to do? grendel|khan July 1, 2005 13:10 (UTC)
I know my haupage dec2000 digital terrestrial decoders acts as a usb ethernet adaptor and it would certainly be possible to make a device that looked like two ethernet adaptors back to back. Plugwash 14:50, 9 February 2006 (UTC)
USB 'laplink' cables exist. However they are quite different from FireWire networking. My understanding is they have chip/s in them to act as devices for each computer (so each comp sees a device). I'm not 100% sure what kind of device. I guess it'll be ethernet but who knows? Perhaps some use COM (serial) or LPT (parallel)? :-P Also see the above on A-A cables... Nil Einne 16:45, 4 August 2006 (UTC) Nil Einne 16:44, 4 August 2006 (UTC)

Terrible USB shape.

My USB plugs seem to migrate and become inserted into my computer's rj-45 (network) jack. I wait for the USB sound, and none... only to find that usb is the same size as the network jack.

Haha, I have done that too! Its funny since most motherboards have the RJ45 jack right next to the usb, when you reach behind to plug in a usb cable, you insert it into the RJ45 Jack. =P

Yes, yes, yes... and it's worse than that, of course. Whose bright idea was it to create a connector that requires (on average) 1.5 attempts to plug in due to its perfectly rectangular shape? Why couldn't "they" make the plug asymmetric and/or rounded so it would guide itself in without my having to look around to the back of the machine and curse at it every time (which for me is about six times every day... grumble)? Rudderpost 03:49, 8 November 2005 (UTC)

Please, try to get back on topic. This page is about the article, not the topic. --Richman271talk/con 00:51, 22 August 2006 (UTC)

removal of information from hid section

I removed this:

If one has the choice of connecting a keyboard to either a USB or a PS/2 port, it is important to determine whether the BIOS supports the USB keyboard when the operating system cannot enter its normal state, because on some older computers an operating system driver is needed to use a USB keyboard. Thus on some computers a USB keyboard cannot be used for troubleshooting when the OS will not start.

because it isn't useful to an encyclopedia article.

  1. Wikipedia is not a troubleshooting guide.
  2. Any machine compliant with PC97 (that's 8 years ago now) supports the USB HID boot protocol. If the HCD never takes control of the bus, the BIOS will keep emulating PS/2 via USB. SchmuckyTheCat 04:21, 28 July 2005 (UTC)
Actually, that will happen only if the BIOS has a "USB legacy support" option for older OSes, which can be disabled on some configuration. I don't know what exactly would happen by having only an USB keyboard, no USB aware OS, and the BIOS set not to provide USB legacy support (or PS/2 emulation): the only workaround would be to reset the CMOS hoping that it auto-detects the USB keyboard, I guess. EpiVictor 15:50, 22 August 2006 (UTC)

Internal USB headers

Can some one please post/write up some information on internal USB headers? There is a lot of information on

  • Maybe this should go on a separate page. Anyway, how in-depth should an article like this be? Seems to me that it should mainly describe what USB is instead of acting as a non-normative adjunct to the standard .. not that an adjunct isn't needed, given the standard's, um, interesting literary style :) --Mpa 19:39, 3 February 2006 (UTC)

Woah, neutrality alert.

Some people don't realize that this isn't an authoritative website, and blindly follow whatever anyone puts up here.

This sentence = removed GET!

  1. We know.
  2. "removed GET"?? What does that mean? — Omegatron 13:37, 29 September 2005 (UTC) same content?

I just noticed that has very similar content / identical for the USB pinout page.


Someone might want to have a look at it. Who copied who? Do they have permission? -- 08:45, 7 October 2005 (UTC)

  • Wholesale plagarism without credit. SchmuckyTheCat 23:10, 7 October 2005 (UTC)

Broken external link

The external link to "Booting Linux from USB" doesn't work...

USB vs Firewire differences

Fixed some problems in the differences section --

"USB supports priority scheduling which can ensure time critical servicing. Firewire devices must compete with all other Firewire devices for every service."

I've removed this; FireWire also has priority scheduling and bandwidth reservation, and was one of the first (maybe *the* first?) busses to offer this. Was definitely the first to offer an isochronous mode.

"USB 2.0 supports split transactions which allow the bus to be used by higher speed devices while slower speed devices are still processing requests. In Firewire all devices must wait for slower devices to complete their transaction before continuing."

Removed. FireWire also supports spilt transactions. This actually comes from IEEE1212, the CSR protocol, also used on Futurebus.

"A USB network relies on a single host at the top of the tree to control the network. FireWire network relies on a more expensive chip inside each device so that any capable node can control the network."

Why "more expensive"? Sounds like somebody's out to get FireWire. There isn't one specific chip, and it's not necessarily more expensive, although it usually is in practice because of lower volume. Edited this, although it's kind of redundant.

"A USB network will provide a minimum power to every device. FireWire devices can optionally provide additional power to the network but in general they don't. Bus powered devices are not common in FireWire (like memory sticks)."

This is untrue; bus-powered FireWire devices are quite common. Also, the first two statements don't make sense. Removed.

"FireWire system performance is affected by the order in which devices are connected. The USB system performance doesn't change with topology -- it is a function of the host and the operating system."

Not true. A USB device separated by the host by a few hubs, or sharing the bus with many other USB devices, will not get as much bus time. The topology does affect things. The FireWire repeater system is actually a little less sensitive in this regard (my opinion). Anyway, removed.

"All forms of FireWire use significantly different, signaling systems than USB. There are some similarities with the cycle and frame markers respectively. FireWire devices have to indicate both the source and destination; USB only requires the destination because the source is always the host."

This is irrelevant -- of course the two busses use different signalling. The second statement is apparently presented as a deficiency of FireWire. Anyway, this bullet isn't needed. Removed.

This paragraph also states that USB 2.0 is faster than firewire. While it mentions that USB 2.0 devices generally don't perform at their maximum speed, it fails to highlight the fact that the average transer rate of an average Firewire 400 device is actually faster than that of an average hi-speed USB device. Jonto 12:16, 3 March 2006 (UTC)
The entire USB vs. FW section is poorly written. It lacks sources, asks rhetorical questions, and focuses to a great degree on theoretical and architectural features, rather than practical ones. It seems to me as if someone wanted to justify the design decisions behind USB 2. Exia 06:42, 2 April 2006 (UTC)
It looks like the article has not been updated since the new version of FireWire came out. On the FireWire article, the theoretical speed is now much faster than high-speed USB. -- Kjkolb 17:31, 24 April 2006 (UTC)

"Other communication options"

If your Operating System and language combination is not supported, another option is a USB to RS-232 bridge. FTDI Chip provides virtual COM drivers with its chips, to make the USB device look to the host software like a COM (RS-232) port.

FTDI produces chips for USB devices that provide RS-232 ports, thus allowing RS-232 devices such as modems to be connected to a computer that has only USB ports available. Consequently, if you have a non-FTDI USB device not supported by your operating system and language, adding an FTDI USB to RS-232 bridge in between won't help you communicate with it. (Besides, the virtual COM drivers are already specific to particular operating systems.) I thus don't see a point in this paragraph. I think it should be clarified or removed, but I hesitate to do the latter as I'd like to keep an "Other communication options" section in some form. 20:07, 1 February 2006 (UTC)

That's very true, Perhaps this paragraph should be re-titled something like "Migration of legacy devices to USB" or "Migration of RS232 devices to USB"?, given the Microchip addition? We could then rewrite it to make that clear.

is it allowed by the spec

to have a cable with a mini-a plug on one end and a full size b on the other? Plugwash 09:29, 29 March 2006 (UTC)

Incompatability issues

Some USB 2.0 controllers don't properly recognize/support some USB 2.0 devices. I have a USB 2.0 to IDE cable, that when plugged into a VIA USB 2.0 controller on a PCI card, is recognized by Windows XP as a USB 2.0 device yet the VIA controller will only operate it in USB 1.1 mode.

Plugged into any other brand of PCI card mounted USB 2.0 controller, it works properly. Plugged into a motherboard mounted port with a VIA controller, it is properly recognized but tends to timeout on transferring large amounts of data.

Neither the manufacturer of the chip in the cable, nor VIA nor Microsoft has addressed the problem. An update to the USB .inf files in Windows 2000 and XP would fix it. Curiously, not even the company that makes the USB 2.0 to IDE chip is interested in doing anything to correct their problem with VIA controllers. "It's Microsoft's problem." is the typical answer. IF an answer can be pried out of Microsoft, it's along the lines of "The manufacturer has to request a fix and must supply information on the problem." VIA is the same, "Not our bag, complain to the device manufacturer and/or Microsoft.".

WHAT IS WRONG WITH ALL OF THEM?! I'd think that when a SERIOUS BUG AND COMPATABILITY ISSUE is brought to their attention, they'd all get in contact to fix it! But nooo, just blow the customer off.

This isn't a troubleshooting site. However, I'll give you these tips:
  1. Your cable probably doesn't have the designed for Windows logo on it, does it?
  2. Does it have the certified USB full speed logo on it? Probably not.
  3. Via controllers have known issues doing bulk data transfer, they were resolved a long, long time ago, but if this only occurs with Via controllers, why is it a Microsoft problem?
  4. Why do you think a change to the inf files would fix it? Inf files are plain text and fairly easy to edit and re-save with a new name and usually have little to do with actual functionality.
  5. To major corporations, a single no-name device that only has problems on a minor subset of controllers is not a serious bug and compatability issue.
Those logos from msft and the USB-IF aren't just their for marketing and branding. They actually say that the device has been tested to minimal levels of quality assurance. Consumers should pay attention to them. SchmuckyTheCat 16:24, 4 April 2006 (UTC)
I would disagree with your Via-MS point. While I don't know the reason for the problem, it's wrong IMHO to state with certainty if only A has a problem with X (B-H are fine with X) then it must be A's problem. Yes we can say it's most likely but we can't state with certainty without knowing the reasons. E.g. , if X programmed the faulty drivers/whatever. Alternatively, if A is doing things according to specs and standards and X is not, then it's arguably still X's problem. Note this doesn't mean B-H aren't doing things according to the specs and standards, it's possible there is a way to do something according to the specs and standards and still work with X. Of course, depending on the relative power of A and X, A might be the one forced to change even if X is at fault but it's still an X problem IMHO. Of course, there are cases when both A and X comply with the specs and standards etc and it's simply an incompatibility that can result. In that case, it's primarily a problem with the standards but since A is the odd one out, they will probably be the ones to have to change, unless of course the specs change so that A is compatible/compliant but X is not (although we come back to the earlier point about B-H and relative power). Nil Einne 17:00, 4 August 2006 (UTC)

Safe To Remove ??!!

Do anybody have information about,what is happen when we click on safe to remove USB device? The action is about the voltage of the USB device or it is a data sent to USB device?

--Hendinejad 10:54, 23 April 2006 (UTC) []

Since it only seems to appear for storage devices i think its almost certainly to do with closing down the filesystem properly. I doubt it actually shuts off the power though it would be interesting to get out a multimeter and find out. Plugwash 13:35, 23 April 2006 (UTC)
It is flushing the cache. Turn off delayed writes in device manager and it might not ever pop up. SchmuckyTheCat 16:03, 23 April 2006 (UTC)


Should someone (I'd be willing) make a writeup about the USB enumeration process? The current link in this article goes to enumeration in the mathematical sense. Would this be useful for wikipedia, or would it be too technical? Menacer 11:19, 24 April 2006 (UTC)

Considering that many aspects of this article are already too technical, I don't see how it would hurt. Just try to write for a lay audience. We really need to break out some of the more technical aspects into a sidebar or something. SchmuckyTheCat 14:27, 24 April 2006 (UTC)

Daisy Chain

The term daisy chain is an inaccurate description of USB topology (it say as much in the Daisy-chain article). I'm going to put up a rewrite of the 'Overview' section. Just thought I'd give a heads up. Treygdor 00:44, 28 April 2006 (UTC)

The "USB-2.0 Logo" shown in the article is actually the USB-1.1 *icon*. The USB *logos* look entirely different, confer to

The USB-2.0 icon is similar to the USB-1.1 icon, but with an additional plus sign "+", confer to

Good observation — Mobius 07:36, 18 June 2006 (UTC)

Somewhat useful spammy stuff

I just noticed a recent series of edits that add information about specific products and companies to the article. Some of them are interesting and/or unique but I don't think they add to a generalist understanding of USB. I'm going to go through the article again in a few days and be hardcore about removing them. I think a lot of it is drive-by additions by well-meaning people and other stuff is astroturfing and isn't going to be controversial to remove. If you watch this page and contributed stuff, speak up. SchmuckyTheCat 21:18, 25 May 2006 (UTC)

Unintelligible Americanisms

The photo displaying the USB cable uses a nickel for scale purposes. What is wrong with a ruler?! considering most of the world doesn't know what a nickel looks like. Therefore more universal measurements of scale (such as the inch and the centimetre) would be more appropriate. Otherwise if you feel there is no need, then leave the nickels out of it.

No one's stopping you from taking your own picture with whatever you want in it. — Omegatron 17:27, 22 August 2006 (UTC)

Firewire section—license fees

The claim is made that: " part due to their per-port license fee (between 75 cents and $1.50 in bulk licenses)...". I think this may be incorrect. According to the following links, the license fee is $0.25 per device.

Perhaps the author was referring to Apple's proposed licensing fees? I'm not knowledgeable enough to correct this, so I'll leave it for someone else.

As far as I can tell from the FireWire page, Apple did indeed initially charge $1.00 per port but this was later changed. While I agree the paragraph needs improvement note that it is clear that we're talking about the past here:
However, FireWire ports were more costly to implement than USB ports, in part due to their per-port license fee (between 75 cents and $1.50 in bulk licenses(disputed—see talk page) ), and the more complex circuitry the controller required.
Nil Einne 15:29, 4 August 2006 (UTC)

Apple Only Charged for Firewire Branded ports it was an IEEE standard and if you called it 1394 license fees were less. Sony i.Link was also an IEEE 1394 format.

As noted in the link above there was confusion that IEEE 1394 ports ware not Firewire (they were, and were common on PC's before USB2.0)

Cable compatability

Are the cables themselves specific to 1.1 vs 2.0, or just the devices? For example, if I have a cable from a 1.1 device, and I use it to connect a 2.0 device, will it be limited to 1.1 speeds? What about hubs? I didn't see this mentioned in the article and I think it's an important point to clarify with respect to backwards compatability.

With 2.0 the USB-IF started a certification process because there were so many crap cables in the marketplace. Hi-speed (2.0) devices are more susceptible to problems with crappy cables. 1.1 cables have the same specifications as 2.0 cables (a little tightening on some areas that were vague) but USB-IF only certifies for 2.0. Of course, any cable vendor can market a cable as "2.0" without the USB-IF logo - caveat empor.
I wrote about hubs nearly two years ago with the differences. I believe that text is still there. I haven't re-read this article in its entirety in months and I'll take a look later. SchmuckyTheCat 21:57, 13 July 2006 (UTC)
Does the same apply to hubs?
USB hub
and read this section of the article: Universal_Serial_Bus#Transfer_speed. Specifically the last paragraph of that section. SchmuckyTheCat 02:05, 14 July 2006 (UTC)
So, if my hardware is usb 2.0, and I use a regular usb cable, the transfer speed will be high speed? --MarioV 21:05, 17 July 2006 (UTC)
No, v2.0 refers to the specification, not the speed - there are slow 2.0 devices. If all ports, hubs and devices are high speed, then you will get high speed. Poor quality cables degrade the speed you end up actually using because of error correction, etc, but it is still high speed. SchmuckyTheCat 21:26, 17 July 2006 (UTC)

USB device not recognized

what does this message means? I got this message when I plug an mp3 player, but when I plug a usb flash drive I got no message on my Windows XP.--MarioV 23:13, 18 July 2006 (UTC)

Clearly it means your operating system (Crapping Windows) does not know what usb device you have just plugged in. Either you USB device has failed or you do not have the correct driver. Cole31337 23:16, 18 July 2006 (UTC)
But I plug the mp3 player to another computer and it works fine, that means that I have to add a new usb ports to my computer?--MarioV 23:22, 18 July 2006 (UTC)
It usually means the device gave a device id of 0000\0000. Unplug the device. Delete setupapi.log. Plug in the device. Read setupapi.log.
This isn't a troubleshooting website. SchmuckyTheCat 00:41, 19 July 2006 (UTC)

This site is just an online store selling USB products. Its products are by no means "unusual". I think it should be removed. Anyone concur? --

Absolutely. Removed. -Seidenstud 04:10, 30 July 2006 (UTC)

Apple USB

Do Apple use UHCI now that they've switched to Intel processors and chipsets? Karsini 17:18, 24 July 2006 (UTC)

Well since the USB is provided by the Intel chipsets I would assume the answer to that is yes. Intel is not going to provide special chipsets for Apple when there is no reason. Nil Einne 16:39, 4 August 2006 (UTC)

Transaction translators

I would like someone to clarily the writeup on how usb hubs operate in a mixed device environment. Could someone explain how the bandwidth would be shared in a typical usb hub usage scenario? Do the multiple low/full ports compete for the bandwidth of one low/full channel or are multiple low/full channels placed on to the hispeed channel and each of the low/full devices have an effective low/full channel to themselves? Say a usb 2.0 (hispeed) hub is plugged into a hispeed port on the computer. Then the following devices are plugged into the hub: 1. high def web cam (hispeed) with mic (low or full), 2. flash drive (hispeed), 3. bluetooth dongle (full speed), 4. sound card (low/full), 5. usb keyboard (low/full), 6. usb mouse (low/full), 7. printer (hispeed) Rearden9 16:16, 26 July 2006 (UTC)

It depends on the hub. Some hubs have one TT. Some have a TT for each port. Think of a TT as a virtual tunnel equivalent to the bandwidth of a full speed controller. If the hub has a TT for each port, than EACH low/full speed device has a tunnel equivalent to one full speed bus. If the hub only has one TT, then all low/full devices compete for one full speed equivalent tunnel.
Moral: If you want to run a lot of full-speed isoch devices, make sure your hub has multiple TT.
Remember in your example that not all bandwidth is allocated equally. Bus priority is control, interrupt, isoch, bulk. The HID (keyboard/mouse) devices in your example are interrupt. They have a miniscule amount of bandwidth reserved for them so what they send is always heard. The audio and camera devices in your example are isoch, when active they will attempt to reserve a percentage of bandwidth. Just because they are high-speed doesn't mean they demand the complete bandwidth of the bus though. The printer, bluetooth dongle, and flash drive are bulk, they cannot reserve bandwidth. They will use opportunistically use whatever is left up to their maximum speed.
This is more explanatory of what is already in the article to that specific situation. Can you point out a way to improve the article after this? SchmuckyTheCat 19:58, 27 July 2006 (UTC)
Thanks for the clarification. I think expanding more on the role of TT like you did, is what the article needs. Knowing (and why) that a hub can be labeled USB 2.0 and that there can be a dramatic difference in performance is important to know. Not to turn this into an FAQ, but is there a simple or better yet, standard method of knowing how many TT are in a hub? Rearden9 20:57, 27 July 2006 (UTC)
I do not know of any way of knowing how many TTs are in a hub. From a consumer (pre-purchase) POV, there may not be any way of knowing. Sometimes the same product has different electronics in it (sucks, eh?). SchmuckyTheCat 22:48, 27 July 2006 (UTC)
I added a bit on transaction translators from what you wrote here. Please take a look at it. Rearden9 14:07, 31 July 2006 (UTC)
It reads fine and correct as a longer explanation of what is already there. This should probably be moved to the USB Hub article though. Our explanation of hubs is longer in this article than the entirety of the article dedicated to hubs. :o. SchmuckyTheCat 18:55, 1 August 2006 (UTC)


Mice and keyboards are frequently fitted with USB connectors, but are generally supplied with a small USB-to-PS/2 adaptor so that they can be used with either USB or PS/2 ports.

While mice have nearly universally moved to USB, I don't think the same can be said for keyboard. Sure there are quite a large number of USB keyboards but there are also quite a lot of PS/2 keyboards still being sold... Nil Einne 15:25, 4 August 2006 (UTC)

Couple of other problems. The adapter should be a PS/2-to-USB, not the other way around. The order it is written is very important; X-to-Y, where X is the device with the incompatible connector, and Y is the resulting connector. From the operating system and USB port point-of-view, the PS/2 device is addressed as a USB device. A USB-to-PS/2 adapter would be one that would allow, for example, a USB camera to connect to the PS/2 port on the PC.
One other thing to point out is that not all PS/2 devices can be connected using a USB adapter. Besides the physical connection, there's also the driver issue. Keyboards and mice, whether they're PS/2 or USB, use the same device protocols to address them (reading key mappings, mouse coordinates, clicking, etc.) But for other propietary PS/2 devices and software, such as a barcode reader and its associated application, the application will have to be re-written to address the USB interface in order to speak with the proprietary PS/2 device. Most pure-Windows applications may be able to adapt with little or no change, but there are still DOS applications in use today within Windows, and they're hardcoded to address the PS/2 port directly. So when purchasing PCs today, it would still be better to buy a PC with a built-in PS/2 port if use hard-coded applications and devices still need to be used. Groink 20:28, 16 August 2006 (UTC)
USB-to-PS/2 adapters also exist, although they only work with keyboards and mice, not cameras. PS/2 barcode readers, I think, use the same protocol as keyboards. ~~ N (t/c) 15:22, 3 September 2006 (UTC)


I removed the line in bold (emphasis added for clarity) below:

Despite all this and despite USB's theoretically higher speed, in real life benchmarks the actual speed of firewire hard drives nearly always beats USB 2 hard drives by a significant margin. In addition to this some operating systems take a conservative approach to scheduling transactions and limit the number of transfers per frame, reducing the maximum transfers from, say, the theoretical 13 per frame to 10 or 9. Therefore if high speed transfer is what you need you should match this with a good host controller and operating system.

There are two problems with this. Firstly it's not really encyclopedic. Secondly what exactly is the definition of a good host controller and especially OS. I assume there is a reason some OS take the conservative approach. If this line could be made more encyclopedic and perhaps more neutral perhaps it would be suitable to be readded.

My suggestion would be

Therefore, if high speed transfer is desired, a suitable host controller and operating system is required.

However I'm a bit tired so I'll let others decide. Nil Einne 16:32, 4 August 2006 (UTC)

Archive old discussion?

This page is 48 kilobytes long. This may be longer than is preferable; see article size.

I don't know what achiving talk pages involves, but I think it is time to entertain that process for this talk page. Looks like I need to read, Wikipedia:How to archive a talk page, but I also wanted to get my intentions logged and in the open. --Charles Gaudette 20:17, 11 August 2006 (UTC)

Unusual USB connectors?

How are "naked" connectors found on some ultra-mini USB flash drives classified? Eg: usb drive pic --Thenickdude 03:40, 15 September 2006 (UTC)

It's just an A plug that is not spec compliant to design. SchmuckyTheCat 15:18, 15 September 2006 (UTC)

This site has a grand total of 5 items "reviewed", all of which are useless devices. Specifically a coffee warmer, a vacuum cleaner, a "pig-radio/speaker", a toy missile launcher and a massager.

All 5 items are listed as "Their best reviewed items" and have no actual review, just a score out of 5. It looks like an attempt to make some quick money with Google Ads. I think it should be removed as there is no useful information. Falcon48x 13:36, 20 September 2006 (UTC)

bulky flash sticks and compilance

from the artiche

"Note that this means a cable provided by the manufacturer of the device, not a generic "USB-compatible extension cable", as, by definition, USB extension cables do not exist"

Is that why bulkier flash sticks often come with an extention cable in the box (which i guess is then treated as a captive cable for compiliance testing just as equipment using custom connectors is)? Plugwash 16:56, 21 September 2006 (UTC)

Do any of them even bother with compliance testing and sport a logo? SchmuckyTheCat 17:47, 21 September 2006 (UTC)