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Date:      Thu, 08 Oct 1998 19:49:44 +1000
From:      Kevin Lam <kevla@studentmail.dis.unimelb.edu.au>
To:        freebsd-hardware@FreeBSD.ORG
Subject:   Re: Full duplex ethernet
Message-ID:  <3.0.3.32.19981008194944.0097da90@studentmail.dis.unimelb.edu.au>
In-Reply-To: <199810072350.NAA20011@pegasus.com>

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At 13:50 10/7/98 -1000, you wrote:
>Which ether-card drivers currently support full duplex?
>
>Recently, someone here said that full duplex for 10Base-T was a waste
>of time.  But after some research it's beginning to look like that's
>not true at all.
>
>10BT switches are available, and cost way less than 100BT switches.
>
>I've gotten reports from several places saying that in practice, switched
>full-duplex 10BT is faster than half-duplex hub-based 100BT.

You might be confusing a few things here. Firstly, full-duplex does not
equate to switching.. however it is usually implemented alongside
switching. It is true that switched 10BT would be faster than hub-based
100BT, but it would hold true even if it was switched half-duplex 10BT. The
vast improvement in performance comes from the switch, which effectively
creates a dedicated point-to-point channel for communications on the
network, being much more powerful than shared 100BaseTX. 

In a switched architecture, collisions, which greatly impact performance,
are almost eliminated, however, the two stations exchanging data could also
collide with each other, even in a switched architecture. Full duplex
merely eliminates this from happening at all (as both may transmit
simultaneously). Switching plays the greatest part in reducing collisions
and segregating communications, then full-duplex forms the icing on the cake. 

Anyway, for what it's worth, the xl driver (3Com Fast EtherLink) has
full-duplex functions at both 10 and 100Mbps listed as available media. 

--
K

"Deliver yesterday, code today, think tomorrow."

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