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I've noticed that transfers between USB 2.0 drives are usually very slow. From what I understand, this is because all USB 2.0 devices connected to the same USB 2.0-host share the same 480Mb/s of bandwidth.
Is it possible to speed this up by using USB 3.0, ie connecting both drives to a USB 3.0 controller (like a USB 3.0 ExpressCard adapter)?
In other words, do USB2 devices get the full, unshared bandwidth each on a USB3 host?
Wikipedia says no, the USB 2.0 signals are not translated to USB 3.0, they are just passed along, so there is still the 480 Mbit/s bandwidth limit: https://en.wikipedia.org/wiki/USB_hub#Transaction_translator
– endolith – 2016-02-04T18:09:24.2237Interesting question! Yes, you're right that the USB 2 controller shares the bandwidth between its devices. – slhck – 2011-05-03T18:25:11.737
12I can't believe I haven't thought of this yet... I'll be benchmarking it tonight. – Supercereal – 2011-05-03T19:02:42.377
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Related: Do I need USB3 sticks to get USB3 speed?
– AndrejaKo – 2011-05-03T19:49:44.567Oooh, interesting question. Obviously they only work at USB2.0 speeds but...yeah! I dunno! I would THINK so but I really have no clue. – Shinrai – 2011-05-03T20:18:19.140
Comment because I don't have facts. Each USB host is a pipe. Assuming that a sewer that is larger than it, and that sewer is not backed up, you will get full throughput. The more toilets you connect to the pipe, running at the same time in this case, the more your USB pipe fills up. Thus you can assume that, if your device actually can use the entire USB2 speed, you will be able to plug in around 5 480Mb/s devices into a USB3 controller without filling the pipe. The underlying tech has not changed in USB 3. Thus, if you plugged in 3 5Gb/s USB3 devices, you'd have the same issues. – Kevin Peno – 2011-05-03T22:47:25.670
1@Kevin: There was a similar situation in the early days of USB 2.0. Some (cheaper) hubs had only one internal USB 1->2 translation unit (shared bandwidth for all usb 1 devices), others had one translator per port (unshared full bandwidth for each). – Martin – 2011-05-03T23:12:24.167
@Martin, I'm sure that's the case and would continue to be so to save cost. Since the underlying hub shouldn't care what the device is, only allow it access to the BW, and since the item itself should be managing it's max speed, then in theory what I said would hold. If the bus is managing the translation (translation of what???) and the number of translators is limited, then yeah...sucks. – Kevin Peno – 2011-05-03T23:17:10.003
@Blomkvist - I don't get the metaphor. – Shinrai – 2011-05-04T16:33:08.503
It's not a metaphor, it's a simile. – Blomkvist – 2011-05-04T17:11:58.030
Interesting concept. @Kyle, did you get around to testing it? I'd like to know the results. – TheEmpireNeverEnded – 2011-05-11T15:37:35.620
The bandwidth limit is per USB2 controller. Most motherboards these days have one controller per port. When low on ports putting your low speed devices like the mouse, keyboard and UPS on a hub leaves other devices like hard drives with a dedicated controller/port each. – Brian – 2011-05-21T01:18:40.283
@Brain: Do you have a source for this? I'm pretty sure that most motherboards contain only one or two controlllers, or at least that was the standard about 1-2 years ago. – Martin – 2011-05-21T08:13:17.137