Gigabit adapters not backwards compatible?

Discussion in 'Asus' started by, Oct 12, 2005.

  1. I have some A8V boards with the Mavell Yukon Gigabit adapter and some a few
    models of the A7V that either have the Yukon or the 3Com Gigabit adapters.
    I am having a really hard time with these working with any switches or hubs
    that are more than a year old. Here are some of the problems I am having:

    1 . On my home computer (A8V Deluxe) I had a Dell True Moble 2300 router
    with 4 port 100MB switch. My Yukon adapter would not work with that. I
    just purchased the new Linksys router that has the ability to use the Vonage
    phone and my Yukon adapter won't work on that 100 MB switch either. I had
    to go buy another NIC.

    2. At work I have a 3 Com Superstack II Switch 1000 which is a 24 port
    100MB unmanaged hub with a 100 MB switch uplink. All of the A7V880 and
    other A7V models with Gigabit adapters from either Yukon or 3Com will only
    connect to the switch at 10MBs.

    On all of these board I tried to manually adjust the settings of the NIC to
    100MB full and also Half duplex but neither would connect. The only switch
    that I have been able to successfully connect these Gigabit adapters to have
    been my 3Com switch 4250. Anyone else having issues with these adapters?
, Oct 12, 2005
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    NewMan Guest

    Just a general comment on Gigabit adapters in general...

    My experience is that you really have to watch the cables! It is for
    this reason that I prefer the Intel Pro 1000 adapters. Install these,
    and then download the Intel "ProSet" from the intel web site.

    The adavanced tools the ProSet provides allows you to diagnose cable
    problems from the computer desktop! You can even have the tools
    display the signal strength! :)

    Since I switched to the Intel Adapters, I have discovered that all of
    my problems were realted to questionable or sub-standard cables in the

    And I find that the gigabit adapters are finicky. If the cable is
    "bad", then it does not matter that you switch the speed down
    manually, it just wont work properly.

    I had the same problem when we went form 10 MBit to 100 Mbit. My
    speculation at that time, and I stand by it, is that the latest
    generation cards are using smaller device geometry in the silicon.
    Smaller devices just cannot push the current required to overcome
    cabling problems - even minor ones.

    Another thing I did, eventually, was ditch an old Hub and replace it
    with a Linksys SR2024 10/100/1000 switch.

    although for home use this would work too:

    We recently upgraded to a gigabit router as well, D-Link DGL-4100:

    With all of these newer devices, connectivity has NOT been an issue.

    In fact I love the new router. It has simplified many tasks. We got it
    for cross-router connectivity at gigabit speeds, we have no use for
    the "gamefuel" stuff.

    NewMan, Oct 12, 2005
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  3. I would rather not just buy new GB cards, new switches, and new cabling. I
    was hoping that there might be a solution to the problem that would allow me
    to keep my current infrastructure. I don't need GB speed but I do want to
    use 100MB.

    The cables going to the switch are all at least CAT 5. Do I have to use 5e
    or 6 even though I am just using a 100MB switch?
, Oct 12, 2005

    NewMan Guest

    What I found with my problem cables was that the stuff in the wall was
    indeed labled "cat5". But what I also found when I ripped some of the
    wire out of the walls was that the contractor who originally did the
    work, long before we came along, had used about the cheapest cable on
    the face of the planet.

    This is akin to "detroit" ratings on car parts. If an alternator on a
    Detroit made car says "80 AMPS", that means 80 amps on the paper of
    some design engieers desk (strictly theoretical maximum). You would be
    lucky to get 80 AMPS out of the alternator at 10,000 RPM, doing 100
    MPH, down hill, and with a tail wind!

    So it can be with other things. My bet is that if you install an old
    PCI based 10/100 NIC in your motherboard that your communitcation
    problems will disappear. If that happens, than you can bet that the
    cable is the problem, even though you are trying to manually set the
    gigabit NICs to 100 Mbps.

    Alternatively, you can always go buy a 100 foot CAT5e cable and us it
    temporarily to see if the problems go away. Kinda rude & crude, but
    inexpensive and it works! ;)

    Also, it is of VITAL importance that the cables be correctly made! If
    you have constructed your own cables, then they may work fine at 100
    Mbps, but if you have not staggered the twisted pairs properly, the n
    they will give you nothing but problems when used with gigabit NICs!
    And in making your cables also note that the RJ-45 connectors MUST be
    the correct oned for your cable! There are two different types, one
    for soldi copper wires, and one for stranded. Use the wrong connector,
    and it wont work properly either.

    If you are still having problems, and the cable is in the wall, then
    you might want to pull off the wall plates and have a look at how the
    cable is connected to the RJ-45 connetors in the wall. When I was
    having problems with one computer, and used the Intel Diags, it told
    me there were missing pairs! When I pulled the wall plate, the phone
    company had used one of the wire pairs to run a phone connection to
    that office! Well at the old 10 Mbps speed, this was not an issue
    because the pairs were not required, but at 1000 Mbps - um Houston, we
    have a problem!

    Contractors are often the worst. If they can cut a corner and save 50
    cents, they will. All that is required is that the work meet the
    functional spec that is in place at the time the work is done.
    Contractors don't give a flying fig about the future, IMHO.

    I have used CAT5e for my 1000 baseT connections, and have NO problems.
    The switch and router upgrades were just bonuses which sped the
    newtork up even more.

    NewMan, Oct 12, 2005

    Paul Guest

    If your motherboard has a Marvell Ethernet chip equipped with the
    VCT (virtual cable tester) feature, you can use that to test
    the Ethernet cable. VCT uses time domain reflectometry (TDR)
    to evaluate in a crude way, the cable impedance, and whether
    the chip considers there is an open or a short in the cable.
    While the cable might not actually be open, or shorted, such
    an indication from the VCT will tell you that the end to
    end impedance of all wiring between the two devices in not

    Paul, Oct 12, 2005
  6. Make sure that the LAN cables are wired properly. Gigabit adapters use
    all 8 wires in the cable whereas 10/100 adapters use only 4. It's
    possible that if the cable is not wired correctly the adapter may not
    work even if the other end supports only 100.
    Robert Hancock, Oct 13, 2005

    milleron Guest

    This is very useful info. Thanks very much for posting it.
    I thought I'd list my experience just for reference. It doesn't
    answer OP's question, but might help in troubleshooting.

    My home was built 13 months ago and wired by a reputable firm. I have
    the same old 10/100 Linksys router (that I brought from my old house)
    in the basement by the cable modem. I originally used a 10/100
    Linksys switch in my office, and both of my A8N-SLI Premium's gigabit
    adapters (Marvell Yukon and nVidia) connected through these devices at
    100 Mbs. I recently upgraded the office switch to a Netgear
    10/100/1000. On this device, both the Marvell and nVidia adapters
    connect perfectly. Both the A8N-SLI Premium computer and the Netgear
    switch indicate 1Gbs connections. The cable in my walls is 5e, as
    are the short cables from the switch to my computers -- all
    store-bought or professionally installed. I have no "Cat 6" cable

    In short, everything works, and all gigabit devices are perfectly
    behaved in their backward compatibility.

    milleron, Oct 14, 2005
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