Subject: Re: DECstation 5000/200 questions
To: None <>
From: Sean Davis <>
List: port-pmax
Date: 06/02/2005 14:12:40
On Thu, Jun 02, 2005 at 02:26:38AM -0400, der Mouse wrote:
> I don't know all that much about the 5000/200 - I've got some pmax
> machines but every time I've dragged them out to try to make one work
> it's been a frustrating struggle and eventually a failure - it's always
> looked like flaky hardware, though it could be flaky software.  But I
> do know something about networking. :-)
> > 2) I haven't used coax for networking in almost ten years.  I've got
> >    all the cable, t-connectors, and such, that I'll need, but due to
> >    my network topology and current lack of console access to the
> >    machine, I am unable to determine if a 10base5 <-> 10base2
> >    tranceiver is getting a link or not.
> There is no such thing as a 10base5 <-> 10base2 transceiver, really.
> You can make such a junction with a completely passive adapter (I've
> done it at a previous workplace); if you do put electronics there, I'd
> argue for calling it a repeater, not a transceiver.
> If you mean an AUI <-> 10base2 transceiver (my 5000/260 has an AUI
> port, thanks to the PMAD-A in it), there is no such thing as "link" in
> the sense you are probably thinking of (as in 10baseT and its
> derivatives like 100baseTX).  Such a transceiver just sends carrier out
> onto the medium and hopes.  About all it can tell is whether it's
> seeing about the right AC impedance and about the right DC resistance,
> and I suspect most of them don't do even that much.  (And of course
> there is signal reception, too, and collision detection, but they
> aren't relevant to sending on a quiet net.)

I guess I mean AUI; I really don't know anything about hardware from that
era :-)

> >    I've got an IBM 8271 10baseT switch as my main backbone at the
> >    moment, and it has an AUI port that I believe I can use to connect
> >    to a trans and then to the DEC.  Is that all I need?
> Yes, if you have a 10base2 transceiver for it, that should be it,
> unless the switch requires some incantation to enable the AUI port.

I've got two 10base2 transceivers (or repeaters, whichever)

> >    I've also got a DEC ThinNet Repeater and a Kalpana 10base5 switch,
> A 10base5 switch?!  Wow.  I thought everything from the 10base5 era was
> AUI and depended on (separate) transceivers to talk to the medium.

I'm guessing it's AUI - as I said, I know nothing about networking from
that era - it's just a huge 3U brick with 15 cards that look almost like ISA
but aren't, and each of them has a DB15F port on the back. I get a link
light hooking up a thicknet cable from one to a 10baseT trans to the IBM
switch, and it calls itself an EtherSwitch EPS-1500. (I call it something
I'd rather avoid using if possible)

> > 4) Should I expect a link light if I just power on the DEC with no
> >    boot device, just the 10base2 connected as (I think) it should be?
> >    In my first trial, nothing lit up other than power on the
> >    transceiver.
> Link light on a 10base2 transceiver?  I have no idea what's going on.
> I just dug through my own collection, and the most lit-up 10base2
> tranceiver I find has just five lights: transmit, receive, heartbeat,
> collision, and a power light (which last changes colour to indicate
> whether heartbeat is on or off).

The one I have has a power LED and *checks* ok, I'm stupid. It's using a
casing that was apparently the same for all CentreCOM transceivers... you
know, has a little yellow painted line next to the green power LED, and then
an orange line where collide would be, and red and blue for where (I guess)
other LEDs would be. But there is nothing there. So no, I shouldn't expect
any kind of light other than the power LED. I'd never looked at it closely
before :-P And my DEC 10base2 transceiver/repeater/whatever only has one LED
that I can see, too. (but it's about five times as big as this one, so it's
probably older. Weighs more, too. DEC really did like to break toes, didn't

I guess we'll find out more when I get the gender changer so I can hook into
serial console. All I know for now is that the little red leds next to the
10base2 port on my DECstation do a little dance when I power it on, but then
all go off. (POST status, perhaps?)