Gigabit or not? SiS 190 integrated ethernet.

[Neil Woolford]

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...

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
>