[rescue] Recommended 13w3 to VGA adapter (Dave McGuire)

[Ron Pool]

I’ve done some research on Sun 13W3 video output and monitor resolution selection.

The Sun Frame Buffer FAQ http://www.sunhelp.org/faq/FrameBuffer.html says that 3 of
the 13W3 pins (3, 8, and 9) are used to tell a frame buffer what resolution should be
output to the connected monitor.  There are tables in the FAQ that show what each
3-bit monitor ID specified for resolution for the following frame buffers: TGXplus
(aka TGX+ or TurboGX Plus), TGX (aka Turbo GX), GXplus, GX, SZ, ZX, S24, or built-in
video on a SPARCStation 20 with a VSIMM installed.  This FAQ also gives details and
scripts for specifying non-standard video settings on a TGX/TGX+ frame buffer.  The
FAQ gives hints on how to change front and back porch for a TGX/TGX+, so you may be
able to shift the image left of right on your screen if it’s a little off.

http://ps-2.kev009.com/rs6000/13w3/13w3_pinout.html says that for Sun 13W3 connectors,
pin 4 is Sense Return and also agrees with the Sun Frame Buffer FAQ that pins 9, 8,
and 3 are for Sense 0, Sense 1, and Sense 2.  From that I believe shorting one or more
of Sense 0, 1, or 2 to Sense Return will let you choose a resolution ID of 0 to 7.
This document also has a table that shows what Sense pins to ground to Sense return
for IDs 0 to 7 and the correspond resolution for a frame buffer that doesn’t seem to
be one of the ones in Sun’s Frame Buffer FAQ.

The cablesonline.com cable W3-606 has 12 DIP switches for configuration of which VGA
signal goes to which 13W3 pin and allows for connecting a VGA monitor to a Sun, SGI, or
IBM Psower PC system.  The switch setting table for the cable doesn’t say whether or
not any of the switches allow for selecting monitor resolution, but I suspect that at
least for use with the Sun the three switches that are listed as being set to ON/OFF
(switches 3, 6, and 7) may be for setting the 3-bit monitor type ID.  I’ve ordered a
couple of these cables and when I get them I’ll use a multimeter to see if those three
switches do allow for grounding or leaving open the three 13W3 pins that are for
resolution identification.

I found several places that have this cable in stock, but the lowest price I found was
$24.99 with free shipping on eBay at https://www.ebay.com/itm/270832512031 .  Google
for “13W3 12 switches” or “13W3 W3-606” and you’ll find other sellers of this cable
including Amazon and cablesonline.com.

I’ve ordered a couple of those 12 switch cables.  When they arrive, I’ll use a
Multimeter to see if those 3 switches (out of all 12 switches) listed as ON/OFF
correspond to the Sense ID pins.  I’ll report back on what I find and hopefully will
be able to report that switches 3, 6, and 7 correspond to Sun’s 13W3 Sense 0, 1, and 2
pins.  And I’ll also report which Sense pin each switch corresponds to.

I did find another useful document -- Solaris Handbook for Sun Frame Buffers
https://docs.oracle.com/cd/E19683-01/817-0438-10/817-0438-10.pdf has a table of
resolution IDs (0 to 7) and the corresponding screen resolutions for TurboGX Plus frame
buffers and also documents some different ways of selecting a resolution other than
what the 13W3 Sense ID pins are specifying.

                                 -- Ron