From owner-freebsd-current  Wed Aug  5 21:25:21 1998
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From: Bill Paul <wpaul>
Message-Id: <199808060425.VAA23145@hub.freebsd.org>
Subject: Re: Etherlink XL driver
In-Reply-To: <Pine.BSF.3.96.980805095600.302a-100000@bright.ny.otec.com> from Alfred Perlstein at "Aug 5, 98 10:04:27 am"
To: bright@hotjobs.com (Alfred Perlstein)
Date: Wed, 5 Aug 1998 21:25:15 -0700 (PDT)
Cc: current@FreeBSD.ORG
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> using the first version of the driver posted on 100mb segement seemed to
> have not great performance.  The admin here said he was able to get
> ~8megs/sec over the segment using Linux and 11megs/sec via Solaris, the
> FreeBSD driver was never over 4.5megs and averaged around 3-3.5.  This is
> ftp transfers.  It seems to grab a LOT of data, then "stall" then grab,
> stall over and over.

Can you describe the system in which the card is installed? What kind
of processor and how fast is it?

> I know this is an older driver, i'll compile him a new kernel with the
> latest snapshot to see if there is an improvement.  Just thought to let
> you know.
> 
> This is on a -current box with a PCI card 905b on 100/TX.  The driver was
> acting in full duplex mode, perhaps it should have been set to half-duplex
> and it was tripping on itself?

The depends. Both sides of the link must match. If the hub (or switch;
you don't say which you're using) is in half-duplex mode, then the
card should also be in half-duplex mode. What happens is that the PHY
(in this case, the built-in autoneg logic on the 3Com chip) may negotiate
a full-duplex link with the link partner, but then the driver has to
look at the state of the link and set the 'fullduplex' bit in the
MacControl register to match. If the physical layer negotiates a
full-duplex connection but the controller chip stays in half-duplex,
you get 'stuttery' performance, especially with TCP.

Make absolutely sure the 3Com and the hub/switch are operating in the
same mode. Use 'ifconfig xl0 media 100baseTX mediaopt full-duplex'
to force a full-duplex link, or 'mediaopt half-duplex to force a
half-duplex link.

-Bill

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