xorg.conf with an external monitor

The recent xorg server does not support the old xinerama setting, precisely Option "MonitorLayout" in the Device Section. The old configuration of xorg.conf are
2007/03/05 - [computer/linux] - Xinerama on Ubuntu 6.10 with open source driver
2008/02/06 - [computer/linux] - modified xorg.conf file

Again....
I spent several days to understand this inconvenient HISTORY about xorg. Finally everthing is o.k. now.

Now,  a part of the brand-new xorg.conf file is

Section "Monitor"
        Identifier      "Laptop"
        HorizSync       28-64
        VertRefresh     43-60
        Gamma           1.0
        Option          "DPMS" "true"
EndSection

Section "Monitor"
        Identifier      "DellE177FPf"
        DisplaySize     339.92  270.336
        HorizSync       30-81
        VertRefresh    56-76
        Gamma           0.9
        Modeline        "1280x1024_75.00"  135.00 1280 1296 1440 1688 1024 1025 1028 1066  -HSync +Vsync
        Option          "PreferredMode" "1280x1024_75.00"
        Option          "RightOf"       "Laptop"
        Option          "DPMS" "true"
EndSection 

Section "Device"
Identifier      "Radeon Mobility X700 (RV410 PCIE)"
        Driver          "ati"
        BusID           "PCI:1:0:0"
        Option          "Monitor-VGA-0" "DellE177FPf"
        Option          "Monitor-LVDS"  "Laptop"
EndSection

Section "Screen"
        Identifier      "Default Screen"
        Monitor         "Laptop"
        Device          "Radeon Mobility X700 (RV410 PCIE)"
        DefaultDepth    24
        SubSection "Display"
                Depth           24
                Virtual         2560 1824
        EndSubSection
EndSection

Section "ServerLayout"
        Identifier      "Default Layout"
        Screen          "Default Screen"
        InputDevice     "Synaptics Touchpad"
        Option          "BlankTime"           "10"
        Option          "Standby"               "20"
        Option          "SuspendTime"       "30"
        Option          "OffTime"               "40"
EndSection

But, The methods which are well-described in the following references are not the solutions to my laptop.

• http://www.thinkwiki.org/wiki/Xorg_RandR_1.2#Using__.24_xrandr
• http://wiki.debian.org/XStrikeForce/HowToRandR12

Now, the classic story is ....


1. Monitor Section

There are two monitors: one is the laptop panel, the other is an external monitor, for me Dell E177FPf.  In the xorg.conf, the gray colored texts are "optional" that is not critical for my machine.

The Dell monitor spec is on http://accessories.us.dell.com/sna/products/Displays/productdetail.aspx?c=us&l=en&cs=19&sku=320-5577 and is listed in the more

Tech Specs

General
Display Type	Flat panel display / TFT active matrix
Width	14.8 in
Depth	5.5 in
Height	15 in
Weight	10.1 lbs
Enclosure Color	Black
Display
Diagonal Size	17"
Viewable Size	17"
Dot Pitch / Pixel Pitch	0.264 mm
Max Resolution	1280 x 1024 / 75 Hz
Color Support	24-bit (16.7 million colors)
Max Sync Rate (V x H)	76 Hz x 81 kHz
Response Time	5 ms
Display Positions Adjustments	Tilt
Signal Input	VGA
Image
Image Brightness	300 cd/m2
Image Contrast Ratio	800:1
Image Max H-View Angle	160
Image Max V-View Angle	160
Video Input
Analog Video Signal	RGB
Expansion / Connectivity
Interfaces	1 x VGA - 15 pin HD D-Sub (HD-15)
Miscellaneous
Cables Included	1 x VGA cable
Flat Panel Mount Interface	100 x 100 mm
Features	Security lock slot (cable lock sold separately)
Power
Form Factor	Internal
Voltage Required	AC 120/230 V ( 50/60 Hz )
Power Consumption Operational	40 Watt
Power Consumption Stand by / Sleep	2 Watt
Environmental Standards
EPEAT Compliant	EPEAT Silver
EPA Energy Star Compliant	Yes
Environmental Parameters
Min Operating Temperature	41 °F
Max Operating Temperature	95 °F
Humidity Range Operating	10 - 80%

DisplaySize is calculated according to http://www.x.org/wiki/FAQVideoModes as

horizontal = resolution*dotpitch = 1280*0.264 = 337.92,
vertical = resolution*dotpitch = 1024*0.264 = 270.336,

or xdpyinfo | grep -B 2 dot

The references suggest to use "gtf" or "cvt" to get Modeline, but I could not get the correct ModeLine by this. Fortunately, I have another linux machine to use the same monitor, I looked into /var/log/X.org.0.log file, then I found the correct modeline.

gtf returns

 gtf 1280 1024 75 -x

  # 1280x1024 @ 75.00 Hz (GTF) hsync: 80.17 kHz; pclk: 138.54 MHz
  Modeline "1280x1024_75.00"  138.54  1280 1368 1504 1728  1024 1025 1028 1069  -HSync +Vsync

cvt returns

 cvt 1280 1024 75
# 1280x1024 74.90 Hz (CVT 1.31M4) hsync: 80.30 kHz; pclk: 138.75 MHz
Modeline "1280x1024_75.00"  138.75  1280 1368 1504 1728  1024 1027 1034 1072 -hsync +vsync

other machine X.org.0.log

(**) NV(0): *Default mode "1280x1024": 135.0 MHz, 80.0 kHz, 75.0 Hz
(II) NV(0): Modeline "1280x1024"  135.00  1280 1296 1440 1688  1024 1025 1028 1066 +hsync +vsync
(**) NV(0):  Default mode "1280x1024": 108.0 MHz, 64.0 kHz, 60.0 Hz
(II) NV(0): Modeline "1280x1024"  108.00  1280 1328 1440 1688  1024 1025 1028 1066 +hsync +vsync
(**) NV(0):  Default mode "1280x960": 108.0 MHz, 60.0 kHz, 60.0 Hz

2. Device Section

Using lspci |grep VGA

01:00.0 VGA compatible controller: ATI Technologies Inc Radeon Mobility X700 (PCIE)

Thus,     BusID           "PCI:1:0:0"

For ATI driver, outputs of the video card are

• LVDS  : laptop panel
• VGA-0 : RGB output

LVDS and VGA-0 are called "outputname" in the man page of xorg.conf (line around 650 man xorg.conf). This can be checked by xrandr -q.

3.  Screen Section

Virtual is calculated  by

Laptop panel is 1280x800, and the dell monitor 1280x1024

1280+1280 = 2560
800+1024 = 1824

4. Final screenshot

...