Re: strange network problem
On Wed, Nov 01, 2006 at 02:24:33PM -0500, Lennart Sorensen wrote:
> > 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).
Europe has unearthed plugs only for double insulated equipment (which
can be recognised by a symbol resembling two squares in each other).
Double insulated equipment comes with the flat unearthed "europlug"
that is supposed to fit in all sockets, earthed or not (except of
course in the UK which uses a different socket).
Note that the europlug is a lot safer than US plugs: with the europlug
it is impossible to touch the life wire through the metal because the
poles are made from plastic with only a small metal tip. The tip is
already well in the socket before it actually connects to the life
wire, the still visible plastic part of the pole can be touched without
hazard. In the US the poles are made from metal so it's quite easy to
hurt yourself (but hey, 110V is a lot "safer").
Most if not all desktop computers aren't officially double insulated so
they need to be earthed and come with an earthed plug. Unfortunately
lots of older houses still have unearthed sockets and the earthed plugs
fit quite easily. Current regulations require earthed sockets in all
new houses (or rather: for all new electrical installations). If you
really don't have a grounded socket for your computers, make at least
sure that the ground wires from all computer equipment is connected to
each other (easy to do with an earthed extension socket). Better is of
course to have the socket replaced by an earthed one.
> 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?
Yeah, I agree the UK system is silly and has ugly bulky plugs. I guess
the idea is to protect the cable from the plug to whatever is connected
to the other end of the cable. That would only make sense if you don't
have fuses in the electrical panel.
> 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.
Europe doesn't need such plugs because over here earth and ground are
two different and unconnected things, whereas in the US and Canada they
are usually connected together at the electrical panel (at least it was
like that in the houses I've seen in New York state). The ground wire
is the ground for the electrical system. It can and is allowed to have
a different potential from the earth (within limits, of course). The
earth wire is connected to the earth by a metal wire burried a couple
of meters deep into the earth.
There are still some places in Europe where you actually have two life
wires operating at 115V wrt to the ground instead of a 230V life wire
and a ground. The reason for this is that if you balance a 3 phase
triangle system properly you don't need the ground wire and hence you
can save 25% on copper wiring. Right now this is seen as dangerous
cause equipment with a single switch can still be life, so houses are
converted to connect to a 3 phase star configuration with ground wire.
(It was however nice cause without a residual current detector you
could run US 110V equipment without a transformer by connecting it to
one of the life wires and earth.)
> 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.
That's possible in Europe because earth and ground are not the same
thing.
> > 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.
If you're using UTP wiring that's not necessary cause UTP has
transformers on each end of the connection in order to avoid ground
loops. For good old thin or thick ethernet wiring you'd better earth
the computers.
> > 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.
Another great card is the Western Digital/SMC WD8013 (or even the 8
bit ISA WD8003). It uses the same 8390 chipset as the NE2k, but its
packet buffer is memory mapped where the NE1k and NE2k have their
packet buffers only reachable through slower IO space. Back in the old
days I could easily flood a thin ethernet using a 8003 in a 386DX40 :)
Erik
--
+-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 --
| Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands
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