modeline help

Ketan Patel kmpatel at
Thu Oct 4 19:10:49 PDT 2007

Help.  I'm trying to configure my Fedora box to drive a
HDTV with the onboard SiS video card.  I can get a video to
display on the HDTV, but not at the native resolution of
the HDTV.  I'm a relative newbie with regards to Xorg, so
please talk slowly.

I'm trying to force the native 1920x1080 resolution with
Modeline (see xorg.conf below).  If used both the modeline
gathered by DDC as well as that generated by gtf.  The
Xorg.0.log file make absolutely no reference my custom
Modeline so I don't whether likes it or not.  I've
tried this using the SiS driver as well as the generic Vesa
driver.  With the SiS driver, the best resolution I get is
1024x768.  With the Vesa driver, the best resolution I get
is 1280x1024.  The follow four notices, in Xorg.0.log, seem
to be most relevant to the problem at hand; however, I
don't know what to do about it:
(II) SIS(0): Replaced entire mode list with built-in modes
(II) SIS(0): Not using default mode "1280x1024" (unknown
(II) SIS(0): Not using default mode "1920x1080" (unknown
(II) SIS(0): Not using mode "1920x1080p" (no mode of this

I need help in understanding two things:  
1. Why should the max resolution be different with the when
specifying the Vesa driver as opposed to the "SiS" driver. 
  I know it's not a hardware or driver, I can drive my CRT
at 1600x1200 with the SiS driver.

2. My understanding is that the use of "Modeline" should
force X into submitting to my will, even if I don't know
what I'm doing.  So why, then, does it seem to ignore me.

Please help.  I would really appreciate some guidance.

Below is the relevant section of my xorg.conf:
Section "ServerLayout"
        Identifier     "single head configuration"
        Screen      0  "Screen0" 0 0
        InputDevice    "Keyboard0" "CoreKeyboard"

Section "Monitor"
        Identifier   "Monitor0"
        VendorName   "Westinghouse"
        ModelName    "TX-42F430S"
        DisplaySize  320        180
        HorizSync    30.0 - 80.0
        VertRefresh  60
# modeline gathered by DDC, according to Xorg.0.log
        ModeLine     "1920x1080p" 148.5 1920 2008 2052 2200
1080 1084 1089 1125 +Hsync +Vsync
# modeline generate by gtf 1920 1080 60  (1920x1080 @ 60Hz)
#       ModeLine     "1920x1080p"  172.80  1920 2040 2248
2576  1080 1081 1084 1118  -HSync +Vsync
        Option       "dpms"


Section "Device"
        Identifier  "Videocard0"
        Driver      "sis"
#       Driver      "vesa"
        BoardName   "65x/M650/740 PCI/AGP VGA Display
        BusID       "PCI:1:0:0"

Section "Screen"
        Identifier "Screen0"
        Device     "Videocard0"
        Monitor    "Monitor0"
        DefaultDepth     24

        SubSection "Display"
                Viewport   0 0
                Depth     24
                Modes    "1920x1080p"

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