Graphics problem on Intel DQ77KB Motherboard - half desktop missing

[Dave Farrance]

I got an Intel DQ77KB Motherboard a year or so back, and my first Linux
installation went fine. But following an update, the monitor only showed
the right half of the desktop space, rendering it almost unusable.

After restoring from backup, I Googled the issue and found a solution. The
board has two video outputs, a DisplayPort and an HDMI port, and if you
connect only to the HDMI port, as I do, then the Intel graphics driver
thinks that the DisplayPort is also connected to a monitor, and assigns
that to the left half of the desktop. The phantom display is disabled by
inserting an /etc/X11/xorg.conf file containing only:

Section "Monitor"
Identifier "eDP1"
Option "Enable" "false"
EndSection

That works, but I can't use almost any recent live-distro boot-from-flash,
because of this. Not Ubuntu, SUSE, or Fedora. The only one that still
works is Debian 7.4, apparently because that has on old version of X,
version 1.12.4. I think that most distros are up to X version 1.15.

I've tried Googling the issue again and now I can't find it. Nobody's
mentioning it now. And yet I believe that the DQ77KB is a popular
motherboard, frequently used in professional applications, and often runs
Linux. So why can't I see plenty of other people with this problem?

Am _I_ likely to be doing something daft? If so, I can't figure out what.

[Dave Farrance]

Dave Farrance <DaveFa...@OMiTTHiSyahooANDTHiS.co.uk> wrote:

>board has two video outputs, a DisplayPort and an HDMI port, and if you
>connect only to the HDMI port, as I do, then the Intel graphics driver
>thinks that the DisplayPort is also connected to a monitor, and assigns
>that to the left half of the desktop.

Never mind. It was a BIOS setting. I didn't spot it until now because
the DQ77KB's BIOS has many tabbed pages, and links on those pages lead to
other pages. Nested three pages deep was a setting "IGD Flat Panel" that
had to be disabled. It seems that the BIOS defaults to assuming that the
DisplayPort is actually an internal connection, permanently connected to a
flat panel, which it isn't in the case of this particular motherboard.

[alexd]

Dave Farrance (for it is he) wrote:

> The phantom display is disabled by
> inserting an /etc/X11/xorg.conf file containing only:
>
> Section "Monitor"
> Identifier "eDP1"
> Option "Enable" "false"
> EndSection
>
> That works, but I can't use almost any recent live-distro boot-from-flash,
> because of this.

For future reference, you can use the CLI tool 'xrandr' to change display
settings.

--
<http://ale.cx/> (AIM:troffasky) (UnSoEs...@ale.cx)
09:17:41 up 118 days, 10:56, 9 users, load average: 0.51, 0.40, 0.35
"If being trapped in a tropical swamp with Anthony Worral-Thompson and
Christine Hamilton is reality then I say, pass the mind-altering drugs"
-- Humphrey Lyttleton

[Dave Farrance]

alexd <trof...@hotmail.com> wrote:

>For future reference, you can use the CLI tool 'xrandr' to change display
>settings.

Before I figured out what was happening, I usually couldn't even start a
terminal with the left side of the desktop missing. But it's fixed now.

On the subject of HDMI and xrandr...

My HDMI monitor initially showed a dreadful greyish black-level and
unsaturated colours. I did a *lot* of Googling to research the issue,
which affected Windows and Linux, ploughing through almost endless threads
about the issue at communities.intel.com with a lot of confusion but
little help especially from the Intel customer-reps, but I finally
discovered what was going on:

Computer monitors with digital interfaces expect a brightness range of
0-255 levels. But the Intel driver compresses that to 16-235 levels on
HDMI ports because that's what HDMI *televisions* expect. Nvidia and AMD,
on the other hand, always use the full 0-255 levels. Some monitors have
an option to switch between "TV" and "computer" levels, but most don't.

So I presume that most people with a computer that uses the Intel CPU's
own GPU, and have an HDMI monitor, simply put up with it and assume that
their monitor is a bit rubbish.

Anyway, put the following command someplace *after* X has fully loaded.
The login managers like lightdm have options for running a script:

xrandr --output HDMI1 --set "Broadcast RGB" "Full"

(replace HDMI1 with whatever the X.org name of your HDMI is.)

(and you can switch back to the default behaviour with
xrandr --output HDMI1 --set "Broadcast RGB" "Limited 16:235" )

[alexd]

Dave Farrance (for it is he) wrote:

> xrandr --output HDMI1 --set "Broadcast RGB" "Full"

Very interesting, I have an Intel GPU laptop at work that is almost
permanently connected to a monitor with HDMI, so I will be testing that next
week. Can't say I'd ever noticed before, however.

--
<http://ale.cx/> (AIM:troffasky) (UnSoEs...@ale.cx)

22:11:01 up 119 days, 23:49, 9 users, load average: 0.60, 0.58, 0.58