kern/64556: [sis] if_sis short cable fix problems with NetGear FA311's

[Bruce Cran]

The following reply was made to PR kern/64556; it has been noted by GNATS.

From: Bruce Cran <bruce.cran at gmail.com>
To: bug-followup at FreeBSD.org, tom at hur.st
Cc:  
Subject: Re: kern/64556: [sis] if_sis short cable fix problems with NetGear 
	FA311's
Date: Sat, 19 Sep 2009 13:52:43 +0100

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 The problem is caused when the CPU can't keep up with packet
 processing, causing an RX overrun to occur.  On a 1.2GHz AthlonXP
 based system I can get errors to occur if for example I run a grep
 over /usr/src - with a 500MHz CPU I guess it would have trouble
 keeping up at all.  With both ttcp's running, 50% of the CPU time is
 taken up processing interrupts from the card.  Not resetting the card
 when an error occurs seems to have no detrimental effect, so I've put
 together a patch which just logs the error in the if_ierrors interface
 field.   The patch also reduces the delay when setting the short cable
 fix from 100ms to 100us.
 
 -- 
 Bruce Cran
 
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