Subject: Re: Serial and SSH - conections over network
To: None <netbsd-users@netbsd.org, port-sparc@netbsd.org>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
List: port-sparc
Date: 07/10/2003 23:50:59
> Why would you ever need to reboot?  I've got a sparc 2 out there with
> 480 days of uptime.

I've seen similar things.  I still have to reboot machines now and
then.  Part of it is because I'm an OS hacker, but there are also
things like power outages, hardware failures, and cats attacking
powerbar switches.  Even software bugs.

> Ethernet != Serial.

Wellll...as you meant it, yes, though Ethernet _is_ a serial medium.

> You can use the same cables, but ethernet needs 4 wires and serial
> really wants 8 (you *might* get away with a 3 wire serial at
> 2400baud).  But 2 CAT5 cables gives you want you want perhaps.

8??  You don't need more than 4 unless you want to do funky things like
use the modem control lines.  If you cheat and skip the protective
ground you can do fine with 3 (but watch out for ground loops).  And
not just at 2400 baud, either; I hardly ever use anything slower than
9600, and at a past workplace we ran "RS-232" lines hundreds of feet
from machine room to offices at 9600 with no shielding and no problems.

Canonical CatV cable has eight conductors, only four of which are
needed for UTP "Ethernet".  The other four could be used for a simple
serial line Just Fine (absent, of course, ground loops and the like -
but even that isn't always a problem; I recall one line that had a
ground loop carrying so much current there were visible sparks upon
plugging or unplugging, but it worked apparently normally).

Not that I necessarily recommend playing fast and loose with the spec.
But I think this "you _might_ be able to run 3-wire at 2400" is
unnecessarily pessimistic.

Even if you can't run simple serial, there are things called short-haul
modems that will work fine, and are designed for just this sort of
thing.

> I've not found garages to be very temperature or humidity stable.
> They get hot and humid or cold and wet.  That's bad for machines.  I
> pulled a Sparc 1+ chassis out of my garage and found rust.

Well, I don't have a garage, but I do agree with the implied caution.

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