VAX DECserver
I got a few of these DECserver 90TL units. They are a neat little device, with 8 RJ45 serial ports on the front, a 10Base-2 port on the top, a power port on the back and also a “hub port” which I’ll gloss over for now.
Power
The power is DEC-custom, 7-pin Mini-DIN and takes 5.1V. This site has the pinout information. Adapters on eBay go for about $60.
Terminal Data Cables
I made special cables to go from the RJ45 serial ports to the DEC MMJ ports on my VT420s and other terminals. I had to get an MMJ crimper, which I also found on eBay, from a company called Paladin. The pinouts are:
Server port, from EK-DSRVE-OM-001 Figure A-1:
| MJ8 Pin | Signal | Direction |
|---|---|---|
| 1 | Rcv Gnd (RXD GND) | – |
| 2 | Rcv (RXD) | into the server |
| 3 | Tx Gnd (TXD GND) | – |
| 4 | CTS | in |
| 5 | RTS | out |
| 6 | Tx (TXD) | out of the server |
| 7 | DTR | out |
| 8 | DSR | in |
Terminal (MMJ) pinout:
| MMJ Pin | Signal |
|---|---|
| 1 | DTR |
| 2 | TXD (out of terminal) |
| 3 | TXD GND |
| 4 | RXD GND |
| 5 | RXD (into terminal) |
| 6 | DSR |
RJ45-to-MMJ wiring, a la DEC’s BN24H office cable:
| Server RJ45 | Terminal MMJ | |
|---|---|---|
| 1 (Rcv Gnd) | <-> | 3 (TXD GND) |
| 2 (Rcv) | <-> | 2 (TXD) |
| 3 (Tx Gnd) | <-> | 4 (RXD GND) |
| 6 (Tx) | <-> | 5 (RXD) |
| 7 (DTR) | <-> | 6 (DSR) |
| 8 (DSR) | <-> | 1 (DTR) |
Unfortunately, that means you have to cross the wires over others on one one side or the other, unlike the simple MMJ cable which just reverses the pins on either side.
Network
Once you get them connected to Ethernet (I used a 10Base-2 to
10Base-T converter), and power them on, they load the software
via DECnet using a protocol called MOP for Maintenance
Operations Protocol. The DEC spec for this is AA-X436A-TK.
It’s a layer 2 protocol, nothing like TCP/IP, but uses raw
Ethernet packets.
Fortunately, I had already installed DECnet on my two VAXen, which enabled this MOP and LAT, the remote loging protocol.
The firmware is available on glaver.org, which is served from the VAX to the DECserver upon startup. If it can’t load the firmware in 30 seconds, though, the DECserver gives up and needs to be rebooted. I can tell it’s loading the firmware because of the data transfer light on the 10Base-2 transceiver.