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Posted by Peter D on 01/21/08 18:35
"Ilya Zakharevich" <nospam-abuse@ilyaz.org> wrote in message
news:fn0gu0$2end$1@agate.berkeley.edu...
> [A complimentary Cc of this posting was sent to
> Peter D
> <please@.sk>], who wrote in article <13p6sjndnmlji49@corp.supernews.com>:
>> In real life USB maximum transfers peak at about 2/3 of that speed. If
>> you
>> research actual test results, you'll often see speeds max out at 1/3 of
>> the
>> max of 480 Mbps. Becasue USB creates a network where every device "chats'
>> with the central "host" (the computer in most cases) USB 2.0 requires
>> more
>> CPU prcesses than
>
> ... Sorry, but the *technical contents* of this is exactly 0.
You say that as if I shold care what you think. If you have Paypal, send me
a quarter. I'll call you the moment I care. :-)
> If you know WHY the throughput is not close to the theoretical maximum,
> please explain.
It's all there. I assume English isn't your first language. So here goes:
The theoretical bandwith (400Mbit/sec) relies on perfect cable length,
perfect cable materials, and perfect hardware acting perfectly while doing
nothing else. The reality is that cables are not perfect, voltage and
signals on the line(s) are not perfect, connectors are not perfect, hardware
is not dedicated, and more than one item on the USB 'network' degrades
performance. Multiple items (even if not in use) degrade performance even
further. USB is inherently "busy" and "chatty". And that makes it useless
for Vidoe transfer if Firewire is available.
HTH
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