DEC 3000 300X/300

From: Patrick Finnegan <>
Date: Tue Dec 31 07:37:00 2002

On Tue, 31 Dec 2002, Bradley Slavik wrote:

> I see how to hook up vt220 with db25 f-f null modem cable, but how does that
> get vt420 hooked up? It appears to have some kind of RJ connecton in back,
> not DB style. Is there a special cable for that?

It's called an MMJ "Modified Modular Jack" from what I've heard. From
memory, the pinout is approximately:

1 Handshaking
2 Data1 +
3 Data1 -
4 Data2 -
5 Data2 +
6 Handshaking

I think that 1/6 are CTS and DTR, or something like that, but for DEC
gear, hardware handshaking lines shouldn't be needed. Data1/Data2 are
Tx/Rx, I'm not sure which is which, but you can use a null modem cable to
figure that out. If you wanna make a DB25 to MMJ cable:

 2 ------------- 2
 3 ------------- 5
 7 --+---------- 3
     \---------- 4

Notice that on the MMJ, pins 3 and 4 are connected together to ground, and
that the 'important' pins are the middle 4 - it's easy to cut a 4wire
modular phone cable in a pinch, trip off the clip on the modular end (like
below) and wire it to a DB25 connector / patch box. Just remember that the
connector won't lock in now, so use something else to hold it in.
  / /
_/_/_ _____
| | ==> | |
||||| |||||

> >
> >> or what
> >> model monitor with keyboard and mouse is this thing supposed to work with?
> > You need a LK201 or LK401 keyboard and a VSxxx mouse. The same keyboard
> > (and mouse) as used on the VT[234]xx terminals and the VAXstations.
> >
> Where do they hook up to? I see on ebay cables with db15 end and 3 bnc,
> keyboard and mouse at the other end. I hook this into back of DEC 3000 where
> it has tablet port? or do I need two separate cables, one for monitor from
> 3w3 connector and one from tablet port for keyboard and mouse?

The cable for the DEC 3000 series has JUST a keyboard/mouse on one end and
DA15 on the other side. Now, be careful, DEC used a DA15 for the console
on most of its machines, but seemed to use a difference cable, and pinout,
for each machine class.

> >> In a typical DEC fashion, in the manual they do not mention model numbers of
> >> monitor to go with it,
> > The video timings for the on board Smart Frame Buffer are:
> > 1024 x 786 _at_ 72 Hz for the 300L
> > 1280 x 1024 _at_ 72 Hz for the 300, 300X, 300LX
> > Any sync on green capable multisync monitor can be used. You just need
> > a 3W3 video cable.
> I have plenty of monitors, but not quite sure what you are saying. Say I
> have monitor with 13w3 connector on back, then I need 3w3 to 13w3 cable and
> monitor is set? Where do keyboard and mouse come into picture? Special cable
> plugging into tablet port (DB15) in back of DEC 3000?

If you want a 3w3 -> 13w3 cable (which I havent seen but you could
probably make yourself), make sure the monitor can do sync-on-green. Your
best bet is to find an IBM Powerdisplay (multisync) or authentic DEC
monitor that has 3 BNC's on it, and a standard 3w3 -> BNCs cable.

BTW, the DA15 "Tablet" port isn't a 'tablet port'. That's supposed to be
a picture of a keyboard ;).

> Sorry for so many questions, but I do not know too much about these machines
> (as if that is not obvious). Still I hope to soon have OpenVMS or Linux
> running on them.

One last note - even though I'm a Linux fan, I seem to remember that
NetBSD is a better OS to use than Linux (of course OpenVMS is also great,
if you can get software for it to do what you want, or wanna spend $$$ or
time doing it). I've got OpenVMS and NetBSD installed on my DEC 3000/600
- on separate drives.

Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
Received on Tue Dec 31 2002 - 07:37:00 GMT

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