U.S.B. speeds

[Giles Orr]

On 15 June 2010 20:30,  <phiscock-g851W1bGYuGnS0EtXVNi6w at public.gmane.org> wrote:
> Because of handshaking and protocol overhead, the effective transfer rate
> over USB is *much* less than the basic speed numbers would seem to
> indicate.
> It also depends on the type of transfer you are doing.
>
> I don't know exact figures, but I do remember that USB 1.0 was in effect
> not all that much faster than a high baud rate serial connection, in the
> order of 100k bytes per second. (I'm going from memory...)
>
> Peter
>
>> How fast is U.S.B. 1 ?
>>
>> How fast is U.S.B. 2 ?
>>
>> What is the ratio of the two speeds ?

"The actual throughput currently (2006)[update] of USB 2.0 high
bandwidth attained with real-world devices is about two thirds of the
maximum theoretical bulk data transfer rate of 53.248 MiB/s, a typical
observation being around 28-29 MiB/s. For USB 1.1, an average transfer
speed of 880 KiB/s has been observed. Typical high bandwidth USB
devices operate at lower data rates, often about 3 MiB/s overall,
sometimes up to 10–20 MiB/s."
   (http://en.wikipedia.org/wiki/Usb#Transfer_speeds_in_practice)

>From personal experience, these "typical" numbers sound slightly low -
perhaps 10%?  But close enough.  The downside of USB to me has always
been that it sucks up all the cycles on your processor.  Bleh.

-- 
Giles
http://www.gilesorr.com/
gilesorr-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org
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