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 From:  =?iso-8859-1?Q?Anders_Nordstr=F6m?= <and at telia dot com>
 To:  <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] Collisions on full-duplex LAN interface
 Date:  Mon, 14 Feb 2005 11:01:05 +0100
Thanks for the further info.

I took Chris Buechler's initial advice to pick up a few used quality NICs 
(3Com and Intel) and it feels like it was worth it. The autonegotiation now 
works and so they're running at full duplex and it's also worth noting that 
CPU utilization went down from about 25% to 7% on a PII 233.


/Anders




----- Original Message ----- 
From: "Fred Wright" <fw at well dot com>
To: <m0n0wall at lists dot m0n0 dot ch>
Sent: Monday, February 14, 2005 5:03 AM
Subject: Re: [m0n0wall] Collisions on full-duplex LAN interface


>
> On Wed, 2 Feb 2005, Chris Buechler wrote:

>> wrote:
>> > I'm worried about the collisions on my LAN interface, since it's full 
>> > duplex
>> > and connected to a gigabit switch. I've read somewhere that there could 
>> > be
>> > problems with the Realtek 8029 chipset, which this NIC has. Could that 
>> > be
>> > it?
>> >
>>
>> The reason is because it's not full duplex.  According to the ed(4)
>> man page, the full duplex mediaopt isn't available on that driver.
>
> Actually, it doesn't explicitly state that full duplex isn't supported; it
> just doesn't mention it at all.  And actually, that part is claimed to be
> handled by the miibus driver.
>
>> Most every ed-based card I've seen has a coax port in addition to
>> RJ45, and coax can't do full duplex, so my educated guess would be the
>> chipset doesn't support full duplex at all (the driver doesn't, at a
>> minimum).
>
> It wouldn't be a good guess in principle, since pretty much any chip that
> uses MII (and some that can't) can interface to coax with an appropriate
> PHY and transceiver.  The typical obstacle to full duplex is that early
> chips (e.g. the 7990) shared some logic (e.g. CRC) between transmit and
> receive.  Newer chips usually support it, but 10Mb-only chips rarely (if
> ever) support autonegotiation, and inexpensive switches rarely (if
> ever) support full duplex without autonegotiation.
>
> And in any case, the 8029 datasheet claims that it supports full duplex.
>
> Fred Wright
>
>
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