13W3 or DB13W3 is a is a particular style of the D-subminature family of connectors. It has the same width as a DB25 connector but instead of 25 small pins it is comprised of 13 total pins, 10 small pins and 3 larger coaxial connectors. This connector is primarily used as an analog video connection for workstation monitors by Silicon Graphics, Sun Microsystems, IBM, Apple Computer and others.
The 13W3 connector has greater noise rejection for the three video signals since the video signals use miniature coaxial connections.
In video use, the 3 coaxial connectors are used for the Red, Green and Blue video signals and the 10 smaller pins used for sync, monitor sense and in some cases DDC.
The 13W3 connector was used by workstations where display resolutions were higher than traditional desktops of the time which were primarily text based. Applications which used 13W3 were previously using separate BNC connections between the graphics generation hardware and display. The 13W3 cable was a single connector instead of 3, 4 or 5 connectors and the molded body is generally more durable than crimped BNC connectors.
Vendors made their own pinouts instead of having a single established standard. This wasn't a problem for users during most of the hardware's first life. In general these users would buy a workstation complete with monitor from a single vendor. Even if there were Sun and SGI workstations in a company, matching monitors were purchased with the workstation and the workstation + monitor was treated as a single unit.
In the second hand market and hobbyist environment the monitors are not always kept together with the workstations and compatibility has surfaced as a issue. New LCD monitors take less space, produce less heat and often have better image quality, especially as the old CRTs are banged up and are out of adjustment.
One frustrating point for hobbyists comes from Sun and SGI monitors being Sony made units which look the same except for logos and color, but not working properly with workstations of another name. Some forum members found that opening the monitor and disconnecting the wires that head to the 10 smaller pins is possible if you can stand to lose monitor sense and have SOG output. You need to accept the risk of electric shock before opening your monitor. Insulating the cable end with good electrical tape so it doesn't flop around is recommended.
Adapters are available from commercial sources to make 13W3 monitors work with VGA (HD15) graphics cards and make VGA monitors work with 13W3 workstations. If you made it this far, you know the obvious caveat is your adapter must match your particular 13W3 application.
VGA to 13W3
These adapters are available, but monitor capabilities are important to consider. Most 13W3 monitors are getting old now and making this translation is less common now. In the past, a discarded workstation monitor was a prized possession to many PC enthusiasts.
Some older monitors may required a composite sync or only use SOG (sync-on-green) and may not work PC graphics cards. Again, pinout is important.
13W3 to VGA
Sun adapters are most popular so if you're using a Sun Microsystems workstation it should be easy to find the right adapter. SGI users are a little less fortunate and are probably in for a bit of a search.
In some cases monitors which can use SOG will work with Sun adapters on SGI workstations without a problem. If you're using a SOG monitor and have SOG output you can remove the 10 smaller pins from your 13W3-VGA adapter.
Otherwise, if you want to build your own adapter, here are the schematics (courtesy of Peter Fuerst)
SGI gfx port | 13W3 DSUB15 | VGA Red Signal | A1 inner -- 1 | Red Input Red Ground | A1 outer -- 6 | Red Ground MonID Bit 3 | 1 NC | MonID Bit 0 | 2 NC 11 | MonID Bit 0 Comp Sync | 3 NC 13 | H.Sync/H+V Hor Drive | 4 -- 13 | H.Sync/H+V Vert Drive | 5 -- 14 | V.Sync MonID Bit 1 | 6 NC 12 | MonID Bit 1 MonID Bit 2 | 7 NC 4 | MonID Bit 2 Ground | 8 NC | Ground | 9 NC | Ground | 10 -- 10 | Logik Ground Green Signal | A2 inner -- 2 | Green Inp/Sync Green Ground | A2 outer -- 7 | Green Ground Blue Signal | A3 inner -- 3 | Blue Input Blue Ground | A3 outer -- 8 | Blue Ground | Shield -- Shield |
The following table summarizes the common pinouts to compare against existing adapters to check compatibility or build your own adapter/cable. If your monitor is capable of Sync on Green you should have no problem connecting only the 3 video signals and ground (A1, A2, and A3). If your monitor requires horizontal and vertical sync signals (H/V) you'll need to connect additional lines. For monitor detection you'll need some more lines, but varies by vendor and whether DDC is supported or not.
|Pin||SGI 13W3||SGI 13W3 (DDC)||SUN 13W3 (SPARC)||SUN 13W3 (older)||VGA|
|1||Mon 3||Data clk. (SCL)||Serial Read||N/C||Red|
|2||Mon 0||Bidirect. data (SDA)||V. sync||N/C||Green|
|3||C. sync||Gnd||Sense 0||Sense 2||Blue|
|4||H. sync||H. sync||Gnd||Gnd||N/C or ID bit 2|
|5||V. sync||V. sync||C. sync||C. sync||Gnd|
|6||Mon 1||DDC 5v+ input||H. sync.||N/C||(Red) Gnd|
|7||Mon 2||DDC Gnd||Serial write||N/C||(Grn) Gnd|
|8||Dig. Gnd||Gnd||Sense 1||Sense 1||(Blu) Gnd|
|9||Dig. Gnd||Gnd||Sense 2||Sense 0||NO PIN (key)|
|10||Dig. Gnd||Gnd||Gnd||Gnd||(Sync) Gnd|
|11||N/C or ID Bit 0|
|12||DDC Data (SDA) or ID Bit 1|
|13||H. sync or C. sync|
|15||DDC Clock (SCL) or ID Bit 3|