From owner-freebsd-hackers  Thu Jun  8 22:20:52 2000
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Date: Thu, 08 Jun 2000 22:21:13 -0700
From: W Gerald Hicks <jhix@mindspring.com>
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To: sthaug@nethelp.no
Cc: hackers@FreeBSD.ORG
Subject: Re: if_dc in v4.0 - Forcing store and forward?
References: <393F33A1.2AE75730@mindspring.com> <37865.960493076@verdi.nethelp.no>
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sthaug@nethelp.no wrote:
> 
> > > I suspect a generic chipset fault, or some design quirk that we are not
> > > working around.  Note that the windoze drivers for these devices put them
> > > permanently in store-and-forward mode.  if_de has the exact same problem on
> > > all of the systems above.
> ...
> > Store and forward mode introduces a horrible performance hit...  Artesyn
> > wouldn't show us the source to their workaround  :-(
> 
> It should be noted that I was able to saturate a 100 Mbps Ethernet with
> FreeBSD 2.2 and a 21140 based card, using around 56% of the CPU of a
> PPro-200. This was done almost exactly three years ago, using the (then)
> standard if_de driver. I have no idea whether the card was operating in
> store-and-forward mode or not - but the performance was perfectly fine.

I can guarantee that it was not running in store and forward mode if you
were exceeding 30 Mbit throughput.

Was this a 21140, 21140A or other stepping?  These variations varied
pretty wildly in their behavior (and I suspect in their actual
implementation as well).

Cheers,

J. Hicks


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