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Date:      Fri, 01 Jul 2011 03:53:07 +0200
From:      Jerome Herman <jherman@dichotomia.fr>
To:        freebsd-questions@freebsd.org
Subject:   Re: trying for 1920x1080 was: Re: Attempting to get an X11 server running
Message-ID:  <4E0D2883.9070807@dichotomia.fr>
In-Reply-To: <20110630214204.219410@gmx.com>
References:  <20110630214204.219410@gmx.com>

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On 30/06/2011 23:42, Dieter BSD wrote:
>>>> Now to see if I can get this wimpy rage xl to do 1920x1080.
>>> Please don't mess with modelines, it should not be needed any more.
>>> Just set the resolutions desired in the Screen/Display section.  If
>>> modelines are really required, get them out of /var/log/Xorg.0.log.
>>> But they almost certainly are not.
>> Though if you *really* wanted to, there's cvt(1):
> The cvt utility helpfully created a couple of modelines which I think
> should work, but Xorg doesn't appear to use it.  I know it sees it,
> because if I put in a typo it complains.  :-)  But the modelines don't
> appear in the log file, even with Option "ModeDebug" and -logverbose 100.
>
> I do get these:
> (II) MACH64(0): Modeline "1920x1080"x0.0  148.50  1920 2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (67.5 kHz)
> (II) MACH64(0): Modeline "1920x1080"x60.0  172.80  1920 2040 2248 2576  1080 1081 1084 1118 -hsync +vsync (67.1 kHz)
>
> but it doesn't use them:
> (II) MACH64(0):<default monitor>: Using hsync range of 30.00-83.00 kHz
> (II) MACH64(0):<default monitor>: Using vrefresh range of 56.00-76.00 Hz
> (II) MACH64(0):<default monitor>: Using maximum pixel clock of 170.00 MHz
> (II) MACH64(0): Estimated virtual size for aspect ratio 1.7778 is 1920x1080
> (II) MACH64(0): Maximum clock: 124.00 MHz
> [ ... ]
> (II) MACH64(0): Not using driver mode "1920x1080" (bad mode clock/interlace/doublescan)
> (II) MACH64(0): Not using driver mode "1280x1024" (bad mode clock/interlace/doublescan)
> (II) MACH64(0): Not using driver mode "1920x1080" (bad mode clock/interlace/doublescan)
> (WW) MACH64(0): Shrinking virtual size estimate from 1920x1080 to 1400x1050
> (--) MACH64(0): Virtual size is 1400x1050 (pitch 1408)
> (**) MACH64(0): *Default mode "1400x1050": 122.0 MHz, 64.9 kHz, 60.0 Hz
> (II) MACH64(0): Modeline "1400x1050"x60.0  122.00  1400 1488 1640 1880  1050 1052 1064 1082 +hsync +vsync (64.9 kHz)
>
> What is this 124.00 MHz clock?  Should I be using 124 or 170?
> The 1400x1050 being 122 makes me think it is using 124 as the limit.
> It isn't clear what it means by "bad mode clock/interlace/doublescan".
> Other rejections have reasons that make sense, "vrefresh out of range",
> "insufficient memory" and so on.
>
> If the pixel clock is the problem, would reducing the color depth help?
It won't, it would help only if your card was short on memory.


WARNING : from there on I am assuming (given the figures from xorg) that 
you are using an old CRT to play with.
If it is an LCD screen, do not try any of the following modelines. LCD 
are tricky beast when it comes to modelines.
Nonetheless even if the modelines I give should be safe, It is 
surprisingly easy to turn an old/cheap CRT monitor into an X-Ray 
emitting bomb. Sure it won't be emitting that much X-Ray, but if you 
spend hours right in front of it... So make sure that the monitor is not 
making strange noises, overheating, or accumulating static after you 
change the modelines.
All this said :

Pixel (or dot) clock is the "speed" at which the video card can provide 
data to the monitor.
Specific time for sync and blanking must also be taken into account.
Your only option would be to :
- go for interlaced mode : Modeline "1920x1080@60i" 77.60 1920 1952 2240 
2272 1080 1104 1110 1135 interlace
- go for low low refresh rate  (48hz - I won't give you the modeline as 
the probablity of damaging your screen are high)
- And eventually decreasing the blanking time/sync time (But it is 
tricky to do, and it can damage monitors)

A must read if you are tweaking monitors : 
http://www.linuxdoc.org/HOWTO/XFree86-Video-Timings-HOWTO/overd.html 
(Old, but the only place where they teach you in detail about dot clock 
problems)

Basically in order to do 1920x1080@60hz you would need 183Mhz of pixel 
dot clock at the very least.

If you are confident that your monitor can take a little bit of shaking 
(It should not harm it - but don't blame me if it does), you could try 
this :

Modeline "1456x819@72" 124.00 1456 1488 1952 1984 819 834 844 860
If you have a good monitor that do not refuses this strange resolution 
right away, you should have a pretty nice picture.



> The xrandr utility doesn't help:
>
> xrandr --fb 1920x1080 -display :0
> xrandr: screen cannot be larger than 1400x1050 (desired size 1920x1080)
>
> xrandr --size 1920x1080 -display :0
> Size 1920x1080 not found in available modes
>
> Current xorg.conf:
>
> Section "ServerLayout"
>          Identifier     "X.org Configured"
> #       Screen      0  "Screen0" 0 0
>          InputDevice    "Mouse0" "CorePointer"
>          InputDevice    "Keyboard0" "CoreKeyboard"
>          # need Option "AutoAddDevices" "Off" to avoid the non-working hald
>          # run moused instead
>          Option "AutoAddDevices" "Off"
> EndSection
>
> Section "Module"
>          Disable  "record"
> EndSection
>
> Section "InputDevice"
>          Identifier  "Keyboard0"
>          Driver      "kbd"
> EndSection
>
> Section "InputDevice"
>          Identifier  "Mouse0"
>          Driver      "mouse"
>          Option      "Protocol" "auto"
>          Option      "Device" "/dev/sysmouse"
>          Option      "ZAxisMapping" "4 5 6 7"
> EndSection
>
> Section "Device"
>          Identifier "Device0"
>          Option "ModeDebug"
> EndSection
>
> Section "Monitor"
>          Identifier "Monitor2220"
>          VendorName "Dell"
>          ModelName  "ST2220T"
>          HorizSync  30.00-83.00
>          VertRefresh 56.00-76.00
>
> # cvt -v  1920 1080 57
> # Warning: Refresh Rate is not CVT standard (50, 60, 75 or 85Hz).
> # 1920x1080 56.90 Hz (CVT) hsync: 63.67 kHz; pclk: 163.00 MHz
> Modeline "1920x1080_57.00"  163.00  1920 2040 2240 2560  1080 1083 1088 1119 -hsync +vsync
>
> # cvt -v -r 1920 1080
> # 1920x1080 59.93 Hz (CVT 2.07M9-R) hsync: 66.59 kHz; pclk: 138.50 MHz
> Modeline "1920x1080R"  138.50  1920 1968 2000 2080  1080 1083 1088 1111 +hsync -vsync
> EndSection
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