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Re: Sluggish transmit completes



USB controller (even hi-speed EHCI) only interrupt the host once per millisecond, so I would expect the average latency on a lightly loaded bus to be 500+ microseconds, which pretty much agrees with your results.

From a USB perspective, you can queue multiple requests (I don't know if your Ethernet device supports that). We will complete them in the order they are queued. You should consider queuing a millisecond or two worth of requests, if you can.

David Ferguson
USB Software Team



At 6:14 PM +0200 10/21/05, Gerald Heinig wrote:
Hi all,

I have a problem with transmit complete calls on my USB Ethernet device. It seems that I have to wait between 300 and 1200 microseconds for my USB write completion routine to get called when I transmit. This is while nothing is going on, no traffic other than my ping.
Is this normal? This seems an extremely long time to have to wait for the transmission of a packet over USB 2.0.
Is there anything obvious I can check that I might be doing wrong?


Cheers,
Gerald
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