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USB 2 Devices Not Necessarily High-Speed
mgcsinc writes "Yahoo is running a story on how some manufacturers of "USB 2.0" devices are making hardware compatible with the USB 2.0 standard, but not necessarily its high-speed component." Sounds like the complaint raised earlier this year.
This explains why I receive a warning message saying "Hi-Speed USB 2.0 device plugged into a non Hi-Speed USB 2.0 port." whenever I plug in my fancy new Nomad JukeBox Zen NX. I tried everything: uninstalling and reinstalling the latest drivers, third-party drivers, microsoft's drivers, different ports on the motherboard...nothing would work. Instead, I had to wait many many hours to transfer my music over to my mp3 player. On the website it doesn't make any distinction between Hi-Speed and Full Speed. Maybe I can return it for false advertising?
Disclaimer: This being /. the above is more with regard to cameras external HDDs, and other hardware which would benefit from the higher speed.
The Mothership
The USB2 does not signify high-speed of course. If you want USB High Speed you need to look for the high speed logo.
as in this image here: http://www.usb.org/images/headermain/2logos.gif
The one on the left is the high speed, one on the right is regular speed. Simple eh?
But is does "go at USB2 speeds": they run at the USB 2.0 "Low Speed" (1.5Mbps).
802.11b runs at 1Mbps, 2Mbps, 5.5Mbps, or 11Mbps. USB 2.0 runs at 1.5Mbps ("Low Speed"), 12Mbps ("Full Speed", what a stupid name), or 480Mbps ("High Speed"). People just need to understand that the name of the standard doesn't relate to a specific transfer speed.
The real problem is if manufacturers don't list on the packaging what actual data rate they do use. Don't support manufacturers that don't provide you the information you want to know.
-Richard L. Owens-Richard L. Owens
Okay, there are two major 'versions' of USB, and three speeds.
USB 1.1 is the 'old' standard. USB 1.1 defined the 2Mb/s and 12Mb/s speeds ('Low speed' and 'Full speed' respectively.) USB 1.1 devices are fully compatible with USB 2.0 devices, but, of course, can only run at 12Mb/s maximum. Note that hubs that are only USB 1.1 compatible will only allow 12Mb/s maximum through them.
USB 2.0 is the current standard. It is fully compatible with Low and Full speeds, plus adds 480Mb/s 'Hi-Speed'. Any USB 2.0 compatible controllers (computers,) can run any device that supports any of the three speeds. USB 2.0 devices that are 'Hi-Speed' are also supposed to support Full speed for compatibility (For example, that 52x CD-RW drive should support Full speed, but will drop to 4x speed, when connected to a USB 1.1 controller.)
The official 'branding' of devices is that they should *NOT* specify USB 1.1 vs. USB 2.0. They should only say the speed they operate at. So Low or Full speed devices (mice, keyboards, printers, etc,) should have a 'USB' logo, with no version numbers, just the USB logo. 'Hi-Speed' devices (hard drives, CD-ROM drives, camcorders,) are supposed to use the 'USB Hi-Speed' logo, which, again, does not say 'USB 2.0', only adds 'Hi-Speed' to the normal USB logo. Companies that use "USB 2.0" branding to advertise any device are not complying with the USB group's marketing standards.
But, yes, a USB 2.0-compatible device can very well operate at 2Mb/s, or 'Low' speed. A good example is keyboards with built-in hubs. My old keyboard is only USB 1.1, so I can plug in any device I want, but it will run at 'Full' speed (12Mb/s) maximum. Newer keyboards have USB 2.0-compatible hubs, so even though the keyboard itself is 'Low' speed, you can plug in your external HD, and the hard drive will happily run at 480Mb/s to your host computer. (Obviously, you also need a USB 2.0-compliant host controller in your computer.)
Another non-functioning site was "uncertainty.microsoft.com."
The purpose of that site was not known.
No, but if someone took a 11 MBit device and labelled it as USB 2.0 then I would not like that at all.
(Now with the new asinine naming convention, USB 2.0 "Full Speed" is actually 11 MBit, so it might not be false advertising.)
You have to look for the "USB 2.0 High Speed" marking to be sure that it's 480 MBit/s.
USB2 IS a protocol, it supports USB1 and USB1.1 protcols
USB2 IS NOT a specific speed
So if claims on a mouse says it supports USB2 but only requires the USB1.1 or USB1 protocol to work, that's okay. However if it says it runs at High Speed USB (400mbps) but really only runs at Full Speed USB (12mbps or what ever it is...) then that's false advertising.
"I just can't sit while people are saying nonsense in a meeting without saying it's nonsense" J Watson, Sci Am 288:(4)51
Funny, my PowerBook G4 has an S-video port on the back . . .
Yes, FireWire is still technically better than USB 2. That extra 80 Mbps isn't impressive when one interface is isochronous and the other isn't. Add to that the massive amount of power, compared to USB 2, that FireWire can provide, and FW's ability to communicate p2p-style directly from device to device, and suddenly USB 2 isn't that impressive.
USB 2 is nice to have, but for high-speed devices like DV cams and large disk arrays, FireWire is king.
Mikey-San
Karma: +Eleventy billion (mostly affected by watching Celebrity Jeopardy)
I develop a number of video products for USB 2.0 and previously USB 1.1. I have some experience of driver development but I am technically a hardware engineer with a leaning towards microcontroller development.
Recently I started developing with USB 2.0 assuming that I could get maybe 50MB/sec data through (480Mbps - overhead) the high speed mode of USB 2.0. Note that full speed is lower than high speed in the spec ?!?!?!?
What I found was that on PCI / cardbus plugin cards, this was actually reduced to about 20MB/sec. This is less than half what you seen on product boxes.
The issue is that host controllers are at fault. USB 2.0 contains a number of slots in each frame on the bus that can be filled with data. If I remember correctly, there are 13 available slots for bulk transfers that can take 512 bytes each. Technically, 12 of these shoulb be the theoratical maximum limit to fill. In practice, many controllers only fill 3 giving the poor bandwidth as they cant keep up with the data rate.
The other issue is with the PCI bus. On many computers this is not fast enough to deal with a single device needing high speed bandwidth although in most cases it does not appear to be the bottleneck.
Most add-on USB 2.0 host controller cards contain a chip from one manufacturer (who I choose not to mention). These suffer the worst performance of 18-20 MB/sec. They comply with the Intel EHCI 0.95 spec for host controllers although the manufacturer has offered a new 1.0 compliant chip offering some increases in speed.
The best performance is when USB 2.0 is tapped from Intel North Bridges on the motherboard. 11 of the slots are filled with data and 35MB/sec can be achieved. Its still not the maximum performance though
If you are buying a PC, make sure you insist on built in USB 2.0 or all your devices may run slow. Also make sure you only use the Microsoft drivers on Windows as they offer significant improvements over others. Win XP or Win2K SP4 contain these.
Note that the USB 2.0 and EHCI 1.0 specs do not contain any specification as to the bandwidth a host controller must provide. Some chips may be better or worse than those mentioned above as there is no control on what a manufacturer should provide
You also forgot to mention that the series of protocols designed for firewire also allow guaranteed delivery of time-sensitive data. You can reserve a portion of that 400 Mbsp bandwidth for video so you don't drop frames. Oh and yes Firewire 800 exists too.
One use for high bandwidth that was missed is scanning. People who used parallel port connected cheap scanners wouldn't notice - if you've used a nice SCSI flatbed you'll know what I mean. I would mention drum scanners but it would take a very warped mind to create a one of those that connected via USB.
USB 1 was a great interface designed by Intrega for low bandwidth devices such as keyboards, graphics tablets, etc. It was bought by Intel who tried to turn it into a high bandwidth bus.
Don't blame me - this
Nitpick, and grossly untrue. As a matter of fact USB2 hubs have a TT controller (transaction tuba or some crap) each port of a USB2 hub acts as a seperate controller to 1.1 devices. That means 4 11Mpbs USB1.1 devices plugged into a USB2 hub each have the full 11Mbps of a seperate bus. You seem to think that version numbers should be used in marketing. The USB-IF has said multiple times that USB2 is not a marketing term.
Low Speed.
High Speed.
Full Speed.
Those are marketing terms, and those are the terms on the USB-IF approved logos. Do you ever wonder why some companies market without logos? Maybe their devices are so broken in their implementation that they can't get a logo. But they go to market anyways. Ouch to you, have fun with your non-compliant devices.