When I first started this whole project I had no idea idea that the old ADC display would be such a PITA to use. But dang-it... it is just so purdy looking. So, one Apple ADC-DVI adapter later, and then one DVI-D-VGA adapter even later... I was ready to start trying to get some visual output from yay-old-Octane2.
So I i've been looking for a display setting to feed into my V6 that would make the display usable. Out of the box, the V6 1280x1024_60 mode(s) work to at least drive the display, but the porch calcs are all skewed, such that the image on screen is shifted so far right and down that the right/bottom 100-200px of the display are hidden.
The native resolution of the display, as some may know, is 1600x1024. As some may also have found, this resolution requires a pixel clock inside the black hole for the v6/v8 boards, so the built-in VFO for that resolution will not actually work (why did they even ship it?).
I am still working on the right settings to accomplish the native display resolution, and may or may not ever get them. I know I can get close, but I won't accept an image with any portion cut-off. So, that is on-going. But I did find that the display will work fine enough at a resolution of 1344x1008. It gets some extra width over the 1280x1024, while sacrificing a little of the height. After _much_ toying around with SwitchResX on my Mac, I was able to get working porch settings, frequencies, etc. for this resolution that put it splat in the middle of the screen (or, well, darn close) and do not crop any edges.
Here are those settings.
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Front Porch: 184
Sync Width: 144
Back Porch: 120
Scan Rate: 60.547
Front Porch: 20
Sync Width: 3
Back Porch: 13
Scan Rate: 57.995
positive sync? Yes
Pixel Clock: ~108.5Mhz (something like 108.49999...)
In theory, with reduced blanking, and with an accepted slight hit to refresh rate (maybe 56hz or 57hz instead of 60hz) I should be able to get a working 1600x1024 resolution. I have one that is mighty close on the Mac, but it still needs tweaking before I try to compile for the SGI.
I am still experiencing an unrelated issue where it appears the monitor or one of the adapters is not happy about SoG... the display color is all green tinted. I know it is not the KVM (NTI ST-4U) - it has worked fine with other displays. I have sorted out custom gamma settings that fix this, but I am not sure how to load them at login... or before...
If anybody has any war stories about these displays, I'd be interested to hear.