Re: [Libusb-devel] Max Data Date Rate ?

[Jeffrey P. <jm...@ya...>]

Thank you for the information

 
Peace,Love,Happiness, and Fun,

Jeff
8558-361-5751





________________________________
From: Tim Roberts <ti...@pr...>
To: lib...@li...
Sent: Tuesday, December 9, 2008 3:47:46 PM
Subject: Re: [Libusb-devel] Max Data Date Rate ?

jeffp wrote:
> I need to tx/rx to/from a box that streams data (in or out) at a max data
> rate of 128,000,000 Bits Per Second.
>
> Does someone know what the maximum data xfer rate (Bits Per Second) that
> libusb 0.9.3 supports for
>
> 1) Bulk Reads  ?
> 2) Bulk Writes  ?
>  

We have sustained more than 40MB/s over bulk pipes for long periods,
which is 320 Mbps.  We've done that with 20 up and 20 down, and with 40
in one direction.  However, this is one area where the chipset matters. 
Some motherboard USB controllers just suck.  There are some host
controllers on which we cannot beat 25MB/s.

> Has anyone written applications that can tx/rx at that rate, or greater ?
>
> Do you think it would be better to use the async bulk transfer functions
> rather than the sync ones ?
> (would they handle the I/O more efficiently/faster) 
>  

You ***MUST*** use asynchronous I/O to get maximum throughput.  USB is a
scheduled bus.  If you do not have a request submitted and waiting at
the time the host controller driver is scheduling the next frame, you
will miss the frame.  That means you must have at least two requests
going at all times.

-- 
Tim Roberts, ti...@pr...
Providenza & Boekelheide, Inc.


------------------------------------------------------------------------------
SF.Net email is Sponsored by MIX09, March 18-20, 2009 in Las Vegas, Nevada.
The future of the web can't happen without you.  Join us at MIX09 to help
pave the way to the Next Web now. Learn more and register at
http://ad.doubleclick.net/clk;208669438;13503038;i?http://2009.visitmix.com/
_______________________________________________
Libusb-devel mailing list
Lib...@li...
https://lists.sourceforge.net/lists/listinfo/libusb-devel