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Re: Slow downloads: NSLU2

On Thu, May 31, 2007 at 11:23:03AM +0200, David Fokkema wrote:
> I know. However, it would be nice to get around 30 Mb/s, which is less
> than 10% of it. When I 'dd', I get around 7 Mb/s with CPU at ~ 80% which
> is almost entirely spent as 'system'. I used:
> dd if=/dev/zero of=test.bin bs=1024 count=102400
> (I just did the test)
> Do you see the same figures? Why is so much time spent as 'system'? I
> would've understood if it was 'wait' or something like that... Don't we
> have DMA?

Remember USB is measured in bits per second not bytes per second, so
480Mbit/s generally only gets about 22MB/s even on a very high end PC due
to whatever overhead is involved in USB.  Firewire seems to be able to
get much closer to its theoretical limits while using a lot less CPU

Len Sorensen

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