Gigabit or not? SiS 190 integrated ethernet.

[Peter Sabaini]

On Sunday 02 December 2007 23:42:55 Neil Woolford wrote:
> Peter Sabaini <peter <at> sabaini.at> writes:
> > On Saturday 24 November 2007 16:58:15 Neil Woolford wrote:
> > > I have an AMD Athlon based motherboard, with a built-in pci ethernet
> > > adaptor that reports itself as a SIS 190 Gigabit ethernet adaptor.
> > >
> > > However, when I connect it to a gigabit switch, it is reported (by the
> > > status led) as a 10/100 device, which is indeed the speed it is clearly
> > > running at.
> >
> > A guess -- the gigabit switch is reporting the actual speed the network
> > is running at, not what the NIC supports.
> >
> > What does ethtool say? Eg. here:
> >
> > # ethtool eth0
> > Settings for eth0:
> >         Supported ports: [ MII ]
> >         Supported link modes:   10baseT/Half 10baseT/Full
> >                                 100baseT/Half 100baseT/Full
> >                                 1000baseT/Full
> >         Supports auto-negotiation: Yes
> >         Advertised link modes:  10baseT/Half 10baseT/Full
> >                                 100baseT/Half 100baseT/Full
> >                                 1000baseT/Full
> >         Advertised auto-negotiation: Yes
> >         Speed: 100Mb/s
> >         Duplex: Full
> >         Port: MII
> >         PHYAD: 0
> >         Transceiver: external
> >         Auto-negotiation: on
> >         Supports Wake-on: g
> >         Wake-on: d
> >         Link detected: yes
> >
> > So its a gigabit port alright, but it autonegotiated a 100Mbit/s
> > connection with my switch. AFAIK many switches operate in an
> > all-or-nothing fashion, ie. if one of their endpoints is 100BASE-TX it
> > will downgrade all ports to 100BASE-TX
> >
> > Note also that 1000BASE-T is sensitive to cabling, so even if standard
> > Cat5 cable should be supported, in practice you'll often have to upgrade
> > to get full speeds (eg. Cat6 / Cat6e)
> >
> > HTH,
> > peter.
>
> The cabling is cat6 between the units that should be able to manage
> gigabit, cat5e elsewhere.
>
> For the built-in adaptor (eth0), despite the term 'gigabit' in its
> identification string, only 10/100 was indicated as possible, not 1000.  So
> that implies the problem lies with that adaptor, whether it just isn't what
> it says it is or whether it needs some driver or tweak to achieve gigabit
> connection.
> 
> The switch I'm using identifies socket by socket for speed, and correctly
> identifies the existing gigabit adaptor on the storage unit I wish to
> connect to.
>
> Adding a very vanilla (cheap) Realtek based pci NIC to the computer results
> in that (eth1) being reported by ethtools as capable of 1000baseT and
> actually being connected at 1000Mb/s speed.
>
> Using this connection is faster than the original 10/100, but only by about
> 20% which isn't the level of advantage I'd hoped for;  I was really
> expecting a two to five times increase in throughput.  (Disconnecting the
> 10/100 leg of the network doesn't appear to improve this.)
>
> So I now need to research the tuning of faster ethernet systems...

What are you trying to do?

In my (limited) experience, actually achieving 1Gb/s througput on "Gigabit 
Ethernet" is not the norm. I had around 900Mbit/s via NFS on two hp DL385 
servers, but only if they were directly connected with a short patch cable 
and after tweaking kernel and NFS parameters.

This link: 
http://www.acc.umu.se/~maswan/linux-netperf.txt

has good tuning tips.

If you are tuning for an internal network, you could also increase your TCP 
MTU, eg. to 9000

peter.


> Neil
>
> > > The computer is running an Ubuntu Gutsy system, updated to current.
> > >
> > > Is there any kind of specialised driver or non-default configuration
> > > needed to get Gigabit speeds out of this adaptor, or is it just
> > > misnamed?
> > >
> > > Neil