[haiku-development] Re: Proposed Change to Common Accelerant for EDID

Axel Dörfler wrote:
Gerald Zajac <zajacg@xxxxxxxxxxxxx> wrote:
[...]
I'm proposing to ignore the refresh rate, and add all modes from the base mode list which have a matching width and height.
[...]
Unless someone can point out any problems with this solution, I will make this change.

That depends on how you intend to implement it, I guess. If you really want to ignore the refresh rate, then I don't think this is a good change - you should only add modes that the current monitor supports, at least.


[...]
After further thought, I have come to the conclusion that 1152x864 is the only resolution that has a problem. After examining the EDID info from 7 monitors, it was found that 6 of the monitors had only one EDID entry for 1152x864 and the refresh rate was always 75Hz. The one exception was an older CRT monitor which had no 1152x864 entry.

The resulting mode list from this EDID info will contain only one entry for 1152x864 which will have a refresh rate of 75Hz; thus, for any refresh rate < 75Hz (eg, 60, 70 or 72Hz), the Screen Preferences computes the pixel clock from the 75Hz entry. This causes some problems with the LCD monitors where the testing was performed. When the mode was set to 1152x864 with a refresh rate of 70 or 72Hz, the display would be offset to the right about 10-20 cm and auto-adjust would not recenter the display. This occurred with ATI (Mach64 & Rage128) and S3 chips. Futhermore, there are some problems at 60Hz where displays from some of the Mach64 chips had some flickering and/or ripples.

If the entries from the Common Accelerant base mode list for 1152x864x60Hz and 1152x864@70Hz are added to the constructed mode list, the above problems do not occur. Thus, I'm proposing to modify the Common Accelerant such that when EDID info is used to build a mode list, it checks the 1152x864 entries in the resulting mode list. If the mode list contains one or more 1152x864 entries, and these entries have refresh rates >= 75Hz, entries for 1152x864x60Hz and 1152x864x70Hz will be added to the mode list.

Best Regards,
Gerald


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