Side note about wrong monitor size [was Re: New monitor, pink vertical line ...]

[Dave Witbrodt]

> Dave> Just for kicks, I removed xorg.conf completely.  The Xorg.0.log
> Dave> files produced were barely different: the changes mostly have to
> Dave> do with autodetection of Default Screen and loss of Monitor
> Dave> sections.  Interestingly, the removal of the Monitor sections
> Dave> causes this change in the Xorg.0.log output:
> 
> Dave>      -(**) RADEON(0): Display dimensions: (593, 371) mm
> Dave>      -(**) RADEON(0): DPI set to (82, 82)
> Dave>      +(==) RADEON(0): DPI set to (96, 96)
> 
> Dave> The first two lines are expected, since I removed the monitor section 
> Dave> that specified the physical size of the monitor.  The line replacing 
> Dave> them ought to be indicating a DPI of 82 since the correct resolution and 
> Dave> screen size are detected:
> 
> Dave>      (II) RADEON(0): clock: 154.0 MHz   Image Size:  593 x 371 mm
> 
> Dave> Instead, either the radeon driver or the X server is altering the 
> Dave> physical screen size to this:
> 
> Dave>      (II) RADEON(0): Setting screen physical size to 508 x 317
> 
> Dave> This also happens with my HD 4850 (even with my old xorg.conf
> Dave> being used) if I use the DVI-to-HDMI converter cable.  With the
> Dave> new HDMI cable being used (on HD 4850), I get the correct
> Dave> physical size: 593x371.
> 
> Dave> Baffling....
> 
> Not really, look at the change in DPI.  I bet that's the difference
> between the 82 and 96 DPI settings. 

Actually, that was my point.  If I use my current xorg.conf, which 
contains information identical to what the X server autodetects about 
the monitor (plus some custom DPMS settings), I get the correct, desired 
DPI of 82.  If I remove xorg.conf, the X server detects all of the same 
info about the monitor (minus the custom DPMS settings), but alters the 
physical size data for some reason and give me the incorrect, undesired 
DPI of 96.

As I mentioned to Alex Deucher, even leaving my own xorg.conf in place 
with the HD 4850:

1.  Using DVI-to-HDMI causes X to alter the physical size, resulting in 
96 DPI.

2.  Using the HDMI cable causes X to use the correct physical size, 
giving me 82 DPI.

Still baffling (to me).


Dave W.