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DB13W3 (also known simply as 13W3) is a particular style of D-subminiature connector commonly used as an analog video interface connector that was used primarily on Sun Microsystems, Silicon Graphics and IBM System p computer workstations, as well as some displays from Apple Computer, NeXT Computer and Intergraph Corporation. The 13W3 connector is no longer used with modern displays, which have generally moved on to VGA or DVI connectors. The DB13W3 connector is also used by some 3Com SuperStack Ethernet switches to carry DC power.

The connector contains 10 standard signal pins and 3 larger positions that can be fitted with either special pins with two concentric contacts for coaxial cable or with special high current pins. When used for video signals on the computer side, the pins are female but the coaxial connectors in the large positions are male. The coaxial connectors carry the video signal split into red, green/gray, and blue; the standard signal pins carry four grounds, three "sense" pins used to communicate with the monitor, vertical sync, horizontal sync, and a composite sync signal.

The 13W3 connector can be converted into a standard VGA connector using cables and adapters that are commonly available. This allows modern multisync monitors, which are common on today's computers, to be used with these workstations as long as they are sync-on-green compatible. Likewise, as many newer Sun monitors support multisync, similar cables can be used to connect them to modern computers.

Even though 13W3 is a standard connector the sync signals are maintained on different pins based on the display and system. Sun Microsystems, Intergraph,[IBM System P Series and SGI have a different set of pins used for the monitor sense IDs and the sync signals. Sun even has two different pinnings: the "classic" one, and one with DDC that was used at least on the UPA graphics adapters (Creator 3D, Expert 3D) and for the corresponding monitors (GD5410, GD5510). This can make matching the correct cable to the monitor virtually impossible. Many monitors with 13W3 connectors do not support separate sync as supplied on most PC systems. Other converters exist to allow connecting newer monitors with VGA connectors to the older systems and workstations. The most popular of these is a cable that allows you to set the sync signals with a series of DIP switches built into the cables.

You need to determine if your monitor is capable of handling Sync-On-Green signals (SOG). If it is, a Sun adapter will work, possibly only with modification. Unfortunately, many more misguided souls bought Suns for some reason, so they are more common. Any adapter advertised "SUN/SGI" on eBay or anywhere else, is a Sun adapter. The SGI gets in there because it may work with a SOG monitor on an SGI.

SOG signaling only requires three connections - Red, Green, Blue - the 3 large coaxial pins on the 13W3 connector. These are common to both the Sun and SGI pinouts, hence the reason they can be used. However, the center 10 pins have alternate sync and monitor ID pins that are not routed correctly for an SGI. With some monitor combinations, they may cause problems. Cutting out these pins and severing the connection will make these adapters work with that SOG monitor. If for some reason you don't believe this works, you have not used an old DEC or similar workstation that only had 3 BNC connectors to the monitor, or hooked up a DVD player to a TV with component video.

If you do not have a SOG capable monitor, you may be SOL. You will need an SGI specific 13W3 adapter that routes the horizontal and vertical sync signals to the appropriate H/V pins on the VGA HD15 connector. This is the common signaling scheme for the PC world. The only places I know for sure that sell appropriate 13W3 adapters were SGI, PCCABLES.COM si87.com may also have something.

Making your own from parts is possible but expensive unless you have a 13W3 cable you want to scrap.

Using a non-SOG monitor with an SGI specific adapter may still have problems, although this is uncommon - the sync signals still present on the green channel can cause issues. It may be possible to disable these sync signals with a setmon command but hasn't been verified.

The el-cheapo SUN/SGI adapters sold on eBay are NOT proper SGI adapters, because they do NOT route the H/V sync for an SGI, and you will need to have a SOG monitor. They were made for SUNs. I'm not saying the SGI doesn't produce H/V sync, I'm saying those adapters do not route/send the signals to the proper pins on the VGA HD15 connector. Read my post about pins 3,4,5 - those are the SGI sync pins, 4 and 5 are H/V sync. SUN uses different pins, so an adapter cannot be both a SUN and an SGI adapter simultaneously (I neglect some expensive adapters that have DIP switches to set the pinouts - thanks recondas for pointing this out!). If your 13W3 routes pins 4 and 5 to pins 13 and 14 on the HD15, you have an SGI adapter. If not, it is probably a SUN or other (IBM, etc.) adapter. Unfortunately SUN adapters are much more common, due to sales volume. It is much harder to find a proper SGI adapter. SUN adapters can be made to work with SOG monitors as described earlier, because you don't need the H/V signals routed and can rely on just the 3 coaxial connections. Or you can break out the soldering iron, as you did, but that's more complicated for a lot of people.

If you have the Sun adapter, cut pins, and a SOG monitor, it will work, unless in the process of cutting pins or something the adapter was damaged in such a way that all three connections are not made. It may be possible that you are set to a resolution the monitor doesn't support, possible the monitor doesn't support the res only in SOG mode. The monitor may also not support SOG even though a datasheet says it does. Note that checking that the monitor works on an O2 is not a check of SOG capability, since the O2 also has H/V sync.

All you need is a sharp and stable xacto knife, a wire cutter and a soldering iron. Not to mention the readiness for some sensibly used violence. You have to cut away all the molded plastic so you can reach the pins. If I remember correctly you only need to deal with the upper row. Then you have to cut the two H and V sync wires and re-route them to the correct pins. Most times you need some wirewarp wire to extend the H/V-wires. If you are done you wrap the inner plastic mold core with a thin layer of insulating tape. The hardest part is to a DSUB-shell which will take the mold core. Industrial or MIL Spec shells are often of the right size, but not exactly cheap...

Pin SGI / DCC Sun
1 Monitor ID bit 3 /
Data clock (SCL)
Ground / DDC-SCL
2 Monitor ID bit 0 /
Bi-directional data (SDA)
Vertical sync / NC
3 Composite sync /
Composite sync
Sense #2 / NC
4 Horizontal drive /
Horizontal sync
Sense ground / DDC ground
5 Vertical drive /
Vertical sync
Composite sync
6 Monitor ID bit 1 /
DDC (+5V input)
Horizontal sync / DDC-SDA
7 Monitor ID bit 2 /
DDC ground
Ground / VSYNC
8 Digital ground /
Sense #1 / NC
9 Digital ground /
Sense #0 /NC
10 Sync ground /
Composite ground
A1 Red Red
A2 Green
(Gray for monochrome)
(Gray for monochrome)
A3 Blue Blue
  13W3                    HD15            Desc.
  A1 inner                1               Red
  A2 inner                2               Green
  A3 inner                3               Blue
  A1 outer                6               Red Ground
  A2 outer                7               Green Ground
  A3 outer                8               Blue Ground
  8                       10              sync ground
  4                       13              horiz./comp. sync
  5                       14              vert. sync

Then set the GFX in the indy to use seperate sync instead of sync-on-green:

 # /usr/gfx/setmon  -s n -v 1280x1024_72

setmon manpage:

          Specifies the source of the sync signal.  syncselect is any
          combination of r, g, b, and a to represent the sync signal on the
          same combination of the red, green, blue, and alpha video cables.
          If  syncselect is n, the sync signal will be generated on the sync
          cable.  If syncselect is not specified, the sync signal will default
          to the green cable.