Forcing a particular modeline ?

[Toan]

Hi

I have an old HDTV with 1080p and 720p. My 1080p display is alright
but I want to use 720p only. However, I get a black screen when I
force 1280x720 mode. My relevant lines in Xorg.0.log is included
below. I notice that there are 2 different modes

[  1730.971] (II) RADEON(0): Modeline "1280x720"x60.0   74.44  1280
1336 1472 1664  720 721 724 746 -hsync +vsync (44.7 kHz)
[  1730.971] (II) RADEON(0): Modeline "1280x720"x60.0   74.25  1280
1390 1430 1650  720 725 730 750 +hsync +vsync (45.0 kHz)

My guess is that xserver-xorg-ati uses the first modeline which my
HDTV doesn't support somehow. I also notice that the second modeline
is the standard ATSC-720p. How do I force xorg to use this mode line
instead of the first one ? They have the same name!

Thanks
Toan


[  1730.970] (II) RADEON(0): EDID (in hex):
[  1730.970] (II) RADEON(0):    00ffffffffffff0034acc13101010101
[  1730.970] (II) RADEON(0):    11110103809051782a7bd1ae4c46a825
[  1730.970] (II) RADEON(0):    0f5054210800d1c08bc0818081c066c0
[  1730.970] (II) RADEON(0):    4bc001000100023a801871382d40582c
[  1730.970] (II) RADEON(0):    45009f295300001e011d801871382d40
[  1730.970] (II) RADEON(0):    582c45009f295300001e000000fd003b
[  1730.970] (II) RADEON(0):    3d0f4411000a202020202020000000fc
[  1730.970] (II) RADEON(0):    004d455553505456390a202020200130
[  1730.971] (II) RADEON(0): Printing probed modes for output HDMI-0
[  1730.971] (II) RADEON(0): Modeline "1920x1080"x60.0  148.50  1920
2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (67.5 kHz)
[  1730.971] (II) RADEON(0): Modeline "1920x1080"x24.0   74.25  1920
2558 2602 2750  1080 1084 1089 1125 +hsync +vsync (27.0 kHz)
[  1730.971] (II) RADEON(0): Modeline "1920x1080"x30.0   74.25  1920
2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (33.8 kHz)
[  1730.971] (II) RADEON(0): Modeline "1280x1024"x60.0  108.00  1280
1328 1440 1688  1024 1025 1028 1066 +hsync +vsync (64.0 kHz)
[  1730.971] (II) RADEON(0): Modeline "1360x765"x59.8   84.50  1366
1432 1568 1776  765 767 772 795 -hsync +vsync (47.6 kHz)
[  1730.971] (II) RADEON(0): Modeline "1280x720"x60.0   74.44  1280
1336 1472 1664  720 721 724 746 -hsync +vsync (44.7 kHz)
[  1730.971] (II) RADEON(0): Modeline "1280x720"x60.0   74.25  1280
1390 1430 1650  720 725 730 750 +hsync +vsync (45.0 kHz)
[  1730.971] (II) RADEON(0): Modeline "1024x768"x60.0   65.00  1024
1048 1184 1344  768 771 777 806 -hsync -vsync (48.4 kHz)
[  1730.971] (II) RADEON(0): Modeline "1064x598"x60.0   50.84  1064
1104 1216 1368  598 599 602 619 -hsync +vsync (37.2 kHz)
[  1730.971] (II) RADEON(0): Modeline "800x600"x60.3   40.00  800 840
968 1056  600 601 605 628 +hsync +vsync (37.9 kHz)
[  1730.971] (II) RADEON(0): Modeline "848x477"x60.0   31.32  848 864
952 1056  477 478 481 494 -hsync +vsync (29.7 kHz)
[  1730.971] (II) RADEON(0): Modeline "720x480"x59.9   27.00  720 736
798 858  480 489 495 525 -hsync -vsync (31.5 kHz)
[  1730.971] (II) RADEON(0): Modeline "640x480"x60.0   25.20  640 656
752 800  480 490 492 525 -hsync -vsync (31.5 kHz)