Created attachment 82302 [details]
Xorg exhibits several problems possibly because of Dual 4550 Radeon cards.
1) 66796 - radeon dual card configure segmentation fault
2) (this bug) - 1920x1080 height too large for virtual size (dual radeon)
3) (after #2 is fixed) xrandr -q lists only one screen for 2 cards, 2 monitors
Much time spent looking for cause why second monitor of a dual radeon (2 cards, 1 monitor each) remained blank when Xorg reported both cards and monitors detected. Monitor on card1 is 1680x1050, monitor on card two is 1920x1080. With no xorg.conf (default config) the 1680x1050 monitor would light up and the 1920x1080 would stay blank. Note the *informatory* message "[585135.723] (II) RADEON(G0): Not using mode "1920x1080" (height too large for virtual size)" in the Xorg.0.log file (in my opinion, if a significant bit of hardware is disabled due to a resource problem, it should be a warning).
A workaround for this problem appears to be to create an xorg.conf file that defines the virtual display size as large or larger than the physical screen size.
Virtual 1920 1088
Virtual 1920 1088
Just remove the Virtual line from your config. If you want to configure multiple cards, you need a zaphod config. e.g., something like:
Option "Xinerama" "on"
# You would need one screen for each monitor
Screen 0 "Screen0"
Screen 1 "Screen1" RightOf "Screen0"
# Actual PCI location of first card/gpu
Option "ZaphodHeads" "DVI-0"
# Actual PCI location of second card/gpu
Option "ZaphodHeads" "DVI-1"
The other possibly related bug reports are:
> Virtual 1920 1088
Did you really mean 1088? Or 1080? (Eighty-eight vs eighty.)
As it is a virtual screen size, does it matter? Yes the physical display only uses 1080, I actually used 1088 in the workaround, which worked. Sorry about entering 3 bugs for one - I didn't know how y'all prefer to deal with that.
Yes, with Alex's suggestion I don't need the virtual display subsections. So Zaphod in this case means dual cards instead of a card with dual monitors? Is this always the case for Zaphod?
So in this case Xorg doesn't auto-config both cards properly (Zaphod options are required but not recognized as needed when no xorg.conf exists).
(In reply to comment #5)
> Yes, with Alex's suggestion I don't need the virtual display subsections.
> So Zaphod in this case means dual cards instead of a card with dual
> monitors? Is this always the case for Zaphod?
It depends what you are trying to accomplish. You need to use zaphod to properly handle multiple cards. You can use zaphod for handling multiple monitors on the same card, but it's not required. Generally for multiple monitors on the same card, you'd use xrandr. zaphod lets you treat each display as a separate X screen, while xrandr treats all displays as a single X screen.
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