SUMMARY: multiple monitors on a Sun FB?

From: Dave Williams (
Date: Mon Apr 12 1993 - 20:59:08 CDT

First, the original question:

> From exudnw Mon Apr 5 12:10:49 1993
> To:
> Subject: more than 1 monitor on sun?
> Content-Length: 337
> Is there any way to drive more than 1 monitor off a single fb? I need to do a
> demo and want to use a Sun 19" color with a Misubishi 37" monster. Has anyone
> done this? What didt you use in the way of cables, etc. Did you use a distribution
> amp? Whose?
> etc..
> etc..
> Thanks in advance.

From: bernards@ECN.NL (Marcel Bernards)

We have a home brewed connector box on which you can attach 4 monitors ( I did not made this one )

The problem with such a box is that it must buffer high bandwith with very little phase shift.

basically it is just a bunch of transistor buffers and some video amps

R-----| |----/////--SCR1
G-----|A B |----/////--SCR2
B-----|M O |----/////--SCR3
H-----|P X |----/////--SCR4
V-----| |

This box is not very good at Sun Supplied video signals, but it works.

I'm planning to build a new one with better components and less parasite capacitance.


Marcel Bernards, UNIX & Net sysadm Netherlands Energy Research Foundation ECN

From: (Koper Zangocyan)


We do demos from time to time on a Sun with two Sun monitors.
Both monitors are Sun3 monitors, which means that they do not have one
monitor cable input, but four. R, G, B, and SYNC

This is the whole trick: We leave the fb output with the ONE monitor cable,
then we attach the ADAPTER from Sun which we have got when upgrading Sun3's
to Sun4's. This adapter cable converts the one fb monitor cable to the
four different cables R, G, B and SYNC.

We have hence 4 cables, there we attach Ethernet T-pieces to all of them,
plug the base of the T to the four plugs of the first monitor, then we continue
with a normal thin Ethernet cable (all four cables the SAME length) to the second
monitor, there we again have 4 Ethernet T-pieces and 4 Ethernet resistances to
cut the circiut. The base of the T's will be plugged to teh second monitor.

Does this help?


From: (Matt Goheen)

We've driven up to three standard Sun 19" color monitors with some
sort of external line amp (I can get the name if you need it, the
stuff is in another room that's locked). The dump little amps
were WAY overpriced (like $400 each) and they use RGB connectors
which means buying cabling too. I think our total cost was around
$600-$800 for each addition monitor.

        - Matt Goheen

From: (Michael J Maciolek)

You can do this without any active hardware if the two displays are
physically close to each other (within 50' or so). Some displays
have a switch to enable/disable their 75-ohm termination. Others,
you would have to take the back off and poke around the video-in

[Insert standard lethal high-voltage-inside-your-monitor disclaimers]

We did this with standard BNC cables and T connectors, putting the
UN-terminated tube in the middle, and the terminated one at the end
of the cable. Worked fine for us.

+------+ +-------+ +-------+
| | | | | |
| |====================| color |=========| color |
| sun |====================|display|=========|display|
| | | | | |
+------+ +-------+ +-------+
                            unterminated terminate

-- Mike Maciolek

From: Randy Born M-50 Rm 266 <>

We use a omputer - video interface ( 1 in, two out ) from Extron Electronics
It cost $600 cdn

It is specifically for a Sparc or Next Colour workstation but other models
exist for other types of suns.

Address of Extron
                                13554 Larwin Circle
                                Santa Fe Springs

                                (213) 802-8804

* Randy V. Born EMAIL: *


slightly changing the requirements, there is a
package called 'xmx' at various sites that supposedly
lets one SUN display everything that another SUN

From: (Russ Poffenberger)

You can do it, but without an amp, the picture gets washed out. Remember the
RGB connections are 75 ohm, 1V P-P signals, and paralleling two monitors cuts
the impedance in half, and the signal amplitude as well. I don't know what
we use for ours though,I am sure any decent one will work.

Russ Poffenberger DOMAIN:
Schlumberger Technologies ATE UUCP: {uunet,decwrl,amdahl}!sjsca4!poffen

From: (David T. Hightower)

We do this all the time with our Mitsubishi XC-3725C; here's how.

We take the output from the SPARC frame buffer (A standard GX), and split the 13WC
connector into four BNC connections: red, green, blue and sync. These get plugged
in the the back of the Mitsubishi monitor, I believe in the RGB1 BNC in ports. The
sync line goes in to either the sync port, or the HD/CS port, depending on your monitor.
Then, set the internal resistance of the red, green, and blue ports to 75 ohm (there
should be a little sliding switch), and the sync port to "normal".

Then, get four more male-to-male BNC cables, and connect from the Mitsubishi to the sun
monitor. If your sun monitor just has the 13WC input connector, you will have to get an

A crude ASCII diagram of the connections, showing what the back of our monitors look like:

        | SUN |
        | 13WC |
                           | |
                           | |
                           | SPLIT |
                             ||+-----------------+ | "H" are the
                             |+------------+ | | Resistance switches: down for
                             +-------+ | | | 75 ohm, up for HIGH (set down,
                                     | | | | since we want 75 ohm)
                                     | | | |
  BACK OF +---------------------------------------------------------------+
  MONITOR | +- O O O O O |
               | RGB1 | H H H H H <- S/G or NORMAL switch |
               | +- O O O O O (this one only) |
               | |
                                     | | | |
                                     | | | |
                                     | | | |
                                     | | | |
                   (to the back of the sun monitor; you may need to go through
                                                                                                                                                                                         another adapter to get it back to the 13WC connector).

This setup works for all 48 systems we have, as well as the Esprit projection monitors we have.
No amplifier is necessary.

A warning: You need to check the refresh rates to be sure they match. We have standard 16"
Sun monitors, and their refresh rate is the acceptable by the Mitsubishi. If there is a
disparity (such as using a 19" 76Hz monitor) then the image will be displayed on one, but not
the other; this occurs because the frame buffer is putting out 76Hz sync signals, which the 19"
can understand but the Mitsubishi can't. The solution to this is to shut the Sun down TOTALLY
(power off), hook the monitors up as described above, then turn the sun on; the frame buffer
will default to the Mitsubishi's refresh rate, and the sun monitor will too.
Hope this helps! Any questions, let me know.

Dave Hightower

From: eeikhey@eeiua (Kevin Heagney)

Hello Dave Williams,
I have not tried this, but I think that the 37-inch Mitsubishi monitor
(66 Hz) just needs an adoptor cable which you could get from a company
called System Video. The cable would then echo the Sun monitor display
onto the 37-inch Mitsubishi monitor.
These monitors would work with a SPARCstation 1 or a SPARCstation 2,
but do not work with an SLC, or an ELC.

From: "J Goldberg" <>

I used a one-in, two-out video amp that I bought thru Andataco. They
had four-out boxes as well. Call Emon Komeily at 510-659-9191 for info.
J Goldberg

From: Larry Weissman 5-2011 <>

We've done this a few times with no problems. You need either old monitors/fb
with the 4 BNC connectors, or new monitors with the BNC<-->13W3 adapters.
SunExpress sells these adapters for $95 (Part 530-1446/A3). I've seen them
cheaper elsewhere(*).

Then all you need is 4 RG59 (75 ohm, I think) coax cables with BNC connectors.
We make these ourselves with our standard thinwire coax tools. They don't even
need termination if the cables are short.

If you need really long cable runs - say 50 feet or more, you may need a
medium speed amp to drive them and might have to use terminators. The local
sun office in Kirkland, Washington (USA) does this to drive a room full of
monitors. You might try the simpler approach first before adding active
amplification, since the cabling needs are similar. I can send you the e-mail
address of someone in the local Sun office if you want to pursue that route.

(*) Nudata, Inc.
    32 Fairview Ave.
    Little Silver, NJ 07739-9976
Larry Weissman Center for Bioengineering, WD-12

From: Gilbert E. Detillieux <gedetil@silver.cs.UManitoba.CA>

We have successfully connected a few Sun SPARCstations, both with color and
mono frame buffers, to both their usual monitor and to projection TV's (some
model of Sony TV, but I don't know which). We had a couple adaptor cables
that connect to the standard Sun video cable, and split into 4 BNC
connectors - we connected one to the frame buffer's video outputs, and one
to the monitor's inputs. In between, we had daisy-chained to the projection
TV, ensuring that the terminators were switched off on the projection TV.
The Sun monitor, which has internal 75 ohm termination, is at the end of the

With this setup, we got a clean picture, and didn't need any sort of amp.
It's important to not have termination switched on for inputs other than at
the end of the chain. This could overload the video outputs.

The hardest part might be to find the adaptor cables. I don't know if Sun
still sells these. We tried to get the D-shell connectors, to make our own
cables (in longer lengths), but couldn't find a supplier for those.

Gilbert E. Detillieux			Internet: <>

From: (Mike Rembis 66520)

Hi Dave....

Our local SUN office has something like this... I believe that they have a splitter from Electrohome....

--- Mike Rembis | Internet:

From: Geert Jan de Groot <>

Snip the terminator resistors in the SUN monitor, and use a tee to connect the video and still have an open end. Then, using 75 ohms, connect to the mitsubishi. terminate that one with 75 ohms on all 4 inputs. DO NOT USE 50 ohm ETHERNET CABLE!

Geert jan

From: apunix!susan@UCSD.EDU (Susan Tornroth)

Try this company: MEGATEK Corp Jim Krasovic 619-455-5590, ext 2120

They make a card I saw demo'd at a local show I was part of, and it seemed to work great.

From: (Frank Greco)

At the Solaris conference last week, the Solaris Eyes demo (very cool) did exactly that. They told me that they simply used a video splitter. I'd try to contact someone in the Solaris Live! (their exclamation, not mine) product area at SMCC.

Frank G.


Thanks to:

bernards@ECN.NL (Marcel Bernards) (Barnes William) (Koper Zangocyan) (Matt Goheen) (Michael J Maciolek) Randy Born M-50 Rm 266 <> (David T. Hightower) eeikhey@eeiua (Kevin Heagney) "J Goldberg" <> Larry Weissman 5-2011 <> Gilbert E. Detillieux <gedetil@silver.cs.UManitoba.CA> (Mike Rembis 66520) Geert Jan de Groot <> apunix!susan@UCSD.EDU (Susan Tornroth) (Frank Greco)

= = = David Williams "You can't win, you can't break even, = = Ericsson Network Systems and you can't quit" = = Richardson, TX 75081 my opinions... =

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