[mosiniak]

Today I had small war with 13W3 to VGA adapter. I realize that there are dozens variants of 13W3 wirings (only RGB are in constant place). Each company has its own standard and several of them has more than one... SGI has two variant (without DDC using ID pins and with DDC using I2C interface). There are also several ways of generating sync pulses (H and V separately, H and V xored together - composite sync or mixed with green signal - sync on green). These all variants multiplied by the number of companies gives dozens combinations. There are also ID pins and they can be configured in several ways multiplying number of possible adapter wiring.

I have a question - in the SGI no DDC 13W3  connector there are 4 "Monitor ID" signals. If I'm right each monitor should set code describing its display capabilities. Using 4 bits it is possible to encode 16 different values. Do You know what each of these values mean?

And second question - are these pins used by graphics hardware, OS or other application? Is it important to set correct ID value?

[mosiniak]

I found here some (unverified) information:

ID pins on a 13W3 connector are (MSBit first) pins 7, 6, 2. Hi-end
machines
want pin 1 Grounded, Indigo2 and Indy want it NC. Gnd means zero, NC
means
1
For Indy, Indigo2:
MonID   monitor guessed
110     Single Scan 1024x768 60Hz 15"
101     Dual Scan 1280x1024&1024x768 60Hz 16"
100     Idem 19"
011     MultiScan 1280x1024&1024x768 21"
010     1280x1024, 76Hz, 16" (82 kHz line freq.)
001     DM-20 MultiScan 1280x1024 76Hz 19" or Single Scan Sony 1280x1024
72Hz
000     1280x1024 60Hz only
111 yields no monitor attached. Default to lowest res / lowest vertical
refresh (if nvram variable ``monitor'' not set to ``H'')

for hi-End
MonID
111     No monitor
110     Single Scan 1024x768 60Hz 15"
010     MultiScan 16"
001     MultiScan 19"

[GRudolf94]

I just wired R, G and B on my lazy cable. Think you can just never bother with those. Works alright so far, across several modes

[mosiniak]

I just wired R, G and B on my lazy cable.  Think you can just never bother with those. Works alright so far, across several modes

I know I can ignore them or try all 16 possibilities. I just want to know what I'm doing and why.