Re: strange network problem
On Wednesday 01 November 2006 16:21, Douglas Tutty wrote:
> My 486 computer (ISA bus) has an internal modem and an ne2000 clone NIC.
> Everything has been fine with this for years.
>
> My new computer ..... accesses the internet via eth0 to the 486
> connected now by cross-over cable after I disconnected the LinkSys
> 10/100 switch while trying to solve this problem.
>
> I'm still in the process of getting things installed on the Athlon via
> aptitude and haven't got xorg working yet although it is installed.
> Until then, I access the Athlon (in the basement) via the 486 (upstairs)
> via ssh.
>
> The problem I'm having is that the NIC on the 486 seems to die and only
> starts to work again after I cycle the power on the 486.
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).
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.
--
AJS
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