Public bug reported:
I have a Gigabyte GA-H87N-wifi motherboard, which explicitly supports 3
monitors at the same time from the motherboards' onboard graphics (2x
HDMI, 1x DVI). The CPU is an Intel 4570S with HD4600 graphics (also
supporting 3 heads at the same time). However, I can only get 2
monitors (any 2, but not all 3) working. All monitors are identical
1600x1200 (NEC LCD2070NX).
The KDE systemsettings GUI helpfully shows icons for all 3 monitors, but
one is always greyed out, and attempting to enable it emits "Failed to
set mode: Invalid argument" in Xorg.0.log. Xrandr compians "Configure
crtc 2 failed". However, it's clear that the graphics hardware can
handle 3 outputs, since it refers to "pipe 0, pipe 1 and pipe 2" in the
logs.
Google doesn't show anything very helpful, except to warn that in older
graphics hardware (definitely not this motherboard) there may be more
output connectors than graphics pipelines, and that in the HD4600 there
are only 2x PLL, so 2 of the monitors need to be identically clocked (as
they are).
This also affects the xorg-edgers packages, as of yesterday, so it seems to be
an upstream problem.
Xorg.0.log attached.
Thanks for your help - please let me know if there's anything I can do
to assist in debugging.
** Affects: xserver-xorg-video-intel (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "Xorg.0.log"
https://bugs.launchpad.net/bugs/1215449/+attachment/3782502/+files/Xorg.0.log
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https://bugs.launchpad.net/bugs/1215449
Title:
triple monitor support not working on HD 4600
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