Re: strange network problem
On Wed, Nov 01, 2006 at 07:22:58PM +0100, Adam Stiles wrote:
> What's changed is that your two network cards are now connected directly
> together, not connected through a switch. It's possible that some strange
> voltages coming out of the Athlon are causing the network card on the '486 to
> go into latch-up.
>
> The input and output circuits of any CMOS IC are designed with diodes to each
> power rail, business ends up, for static protection. In normal circumstances
> both are reverse biased. If a negative voltage is applied, the bottom diode
> goes forward-biased and clamps it to -0.7V. If a voltage greater than +5V is
> applied, the top diode goes forward-biased and clamps it to +5.7V. Except
> these aren't just ordinary diodes; they're more like a sort of cross between
> a zener diode and a triac, and if you stick enough current through them while
> forward-biased and maintain it for long enough then they stay conductive ever
> after, or at least until you cut the power.
>
> One cause of these voltage spikes can be poor bonding between equipment
> chassis. The metal chassis of a computer case is connected to mains earth.
> If the earth connection is sound, the two chassis should be at the same
> potential.
>
> Now, I notice from your e-mail address that you're in Canada, where they don't
> have quite as sophisticated an electrical system as we have here in the UK
> (all wall sockets earthed and individually switched, all plugs non-reversible
> and fused in the live phase, all sockets wired in one big ring).
Plugs here are earthed (unless very old), unlike many places of europe
that only recently started doing such things (say denmark for example).
I have never understood why the brits believe every plug needs a fuse in
it. Makes the plugs rather expensive, and the device ought to already
have a fuse, as should the electrical panel of the house. Does anyone
else on the planet use that system? Our plugs also can not be reversed
unless the device was designed with a plug that specifically can be
reversed. Again I know denmark that isn't the case. On the other hand
denmark typically has residual current detector breakers, which we only
seem to use in bathrooms and such here. Why we don't use them here I
don't really know.
> First, make sure the power sockets serving both computers are properly
> earthed -- preferably using the proper test equipment. If there is a
> problem, get it fixed as soon as possible because it could be a death trap.
> Second, try running both computers from the same power socket, via a long
> extension lead.
>
>
> Even if your network card is permanently damaged, NE2K-alike cards with the
> old 16-bit connector are still available second-hand for not much money.
> Realtek 8019 or 8029-based cards work well.
My 8019s did not work well. My 3c509 on the other hand does work well.
--
Len Sorensen
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