From: andy@ie.utoronto.ca (Andy Sun)
Subject: Re: Centris 650 to Decstation E-net adapter
Organization: University of Toronto, Department of Industrial Engineering
Lines: 86

>pnsf01dw@smucs1.umassd.edu (Dennis J. Wilkinson) writes:
>Not necessarily a thrid-party adapter; Apple does manufacture transceivers
>for thinWire and 10BaseT (twisted pair) cable media, as well as an AUI
>(Attachment Unit Interface) transciever. They run at ~$100 each. If you use
>thinWire or 10BaseT, you'll probably also need terminators (Apple's
>transceivers are self-terminated, if I remember correctly, but I have no
>idea about DECs). 

The third-party media adapters are usually cheaper (at least in Toronto) than
Apple's. I bought the adapters from Asante instead of Apple.

gurman@umbra.gsfc.nasa.gov (Joseph B. Gurman) writes:
>    The DECstation 5000 Models 200 and 240 come with ThinWire only
>(can't say for certain about the Models 125 and 133), so your best bet

That's not true. Only the DECstation 5000/200 comes with a Thinwire
(BNC, coaxial) Ethernet connector. The 5000/25, 5000/133 and 5000/240
all have a single 15-pin AUI Ethernet connector only. I distinctly
remembered this because when got the 5000/200 first and I thought all
of them are going to be Thinwire. I eventually had to go back and ordered
DESTAs (DEC's oversized version of an AUI-to-BNC adapter that MUST be used
with a transciever cable) for the rest of the stations.

My advise to the very original poster (Beverly?) is:

(1) If all you want is to create a LAN with two workstations and won't add
    machines to it EVER, go for Thinwire regardless of the media type. Going
    for UTP (unshielded twisted pair) wiring requires a concentrator which
    means extra money and I believe these units come with at least 6 ports.
    As for Thicknet, it's a nightmare and cabling is expensive. Avoid it
    unless you have no choice (e.g. the two machines are two floors parts).

(2) On the Mac side, you will need:
    - one Thinwire media adapter (from Apple or third-party).
    - MacX (make sure you get version 1.2; 1.1.7 won't run on System 7.1).
    - MacTCP (which comes with MacX; if you get MacX v1.2, you should be
      getting MacTCP v1.1.1 with it. Don't use earlier versions on a Centris).
    - you may or may not need a 25ohm terminator depending on the
      Thinwire media adapter. So just ask the sales if the adapter is
      self-terminated or not.
    - configure MacTCP to use "Ethernet".

(3) On the DECstation side, you will need:
    - for a Model 200, you will only need a T-connector.
    - for Models 25, 125, 133, 240, you will need an AUI-to-BNC adapter.
      Get one that can be plugged in directly to the AUI port of the
      DECstation. This way you save the cost of a transciever cable
      (a 15-pin AUI male to a 15-pin AUI female cable).
    - get a 25ohm terminator.

Your two-machine network will look like this:


       ##T----------------------------------------------[]
      +-----+                                           |
      |     |                                           |
      +-----+                                         +-----+
                                                      |     |
                                                      +-----+
    DECstation                                        Centris
     5000/200                                           650
                              OR

       ##T----------------------------------------------[]
        {=}                                             |
      +-----+                                           |
      |     |                                         +-----+
      +-----+                                         |     |
                                                      +-----+
    DECstation                                        Centris
5000/25,125,133,240                                     650
         
   ##    -> 25ohm terminator
   T     -> T connector
   ---   -> Thinwire (RG58 coaxial cable)
   {=}   -> AUI-to-BNC (i.e. Thick-to-Thin) adapter
   []    -> Thickwire media adapter (assuming self-terminated)
   |
   |

Andy
-- 
Andy Sun (andy@ie.utoronto.ca)          4 Taddle Creek Road, Toronto
Computing Coordinator                   Ontario, Canada. M5S 1A4
Department of Industrial Engineering    Phone: (416) 978-8830
University of Toronto                   Fax:   (416) 978-3453
