Created attachment 20003 [details]
contains 4) xorg.conf_sid6.9.0-1+lenny4_1920x1440_work.txt and 5) Xorg.0.log_git_081102_2560x1600_black_screen.txt

Hi,

Some video modes lead to:
- a black (blank) screen.
- a flickering screen (means, the screen appears shortly, then turns black, reappears shortly...)

Radeon driver regress: Git version is worst than Debian sid driver. (Also radeonhd leads to black screens)

Hardware proved to work at 2560x1600 => look like a driver problem.
   I tried in past
   - with an nvidia card. 2560x1600 worked well with nv driver.
   - with the same radeon 3450 under windows. 2560x1600 worked well.

[Connection]
   HIS HD 3450 Silence 512 Mb => Radeon 3450 (RV620LE) supports up to 2560x1600
   |
   dual-link DVI cable
   |
   monitor dell 3008WFP => flat screen with native resolution of 2560x1600

[Tested drivers]
- sid = xserver-xorg-video-radeon 1:6.9.0-1+lenny4 from Debian sid
- git = radeon git downloaded on 02-Nov-2008

[Result notations]
- F=flicker, means, the screen appears shortly, then turns black, reappears shortly...
- B=black screen, screen does not appear at all (based on min. 1 min test).
- w=works fine (based on min. 1 min test).

[Results]
Resolution Frequency (as listed by xrandr): results
2560x1600 59.9: sid=B  git=B with for git monitor messages 'entering power save' and just enter a few s before waking up again.
1920x1440 60.0: sid=w  git=B with for git many monitor messages 'entering power save' but in fact never enters
1600x1200 85.0: sid=w  git=B
1280x1024 85.0: sid=w  git=w
1280x768  60.0: sid=F  git=F
1024x768  85.0: sid=w  git=w
1024x768  60.0: sid=w  git=w

[Below sections may help to understand why]
1) xrandr shows proposed video modes 
2) Radeon 3450 details 
3) dell 3008WFP details 
4) xorg.conf
5) Xorg.0.log after setting xorg.conf to radeon and 2560x1600 with radeon git of 02-Nov-2008

Regards,
Franck

1) xrandr shows proposed video modes -------------------------------------------------------------
$ xrandr
Screen 0: minimum 320 x 200, current 1920 x 1440, maximum 2560 x 1600
DVI-1 connected 1920x1440+0+0 (normal left inverted right x axis y axis) 641mm x 400mm
   1920x1440      60.0*+
   2560x1600      59.9 +
   2048x1536      60.0  
   1856x1392      60.0  
   1792x1344      75.0     60.0  
   1920x1200      72.8     59.9     60.0     60.0  
   1600x1200      85.0     75.0     70.0     65.0     60.0     59.9  
   1680x1050      60.0     60.0  
   1600x1024      60.0  
   1400x1050      85.3     74.8     70.0     60.0  
   1280x1024      85.0     75.0     59.9     60.0  
   1440x900       60.2  
   1280x960       85.0     60.0  
   1280x800       59.8     60.0  
   1152x864       85.1     75.0     74.8  
   1280x768       60.0  
   1280x720       59.9  
   1152x768       54.8  
   1024x768       85.0     75.1     75.0     70.1     60.0  
   832x624        74.6  
   800x600        85.1     72.2     75.0     60.3     56.2  
   640x480        85.0     75.0     72.8     75.0     60.0     59.9  
   720x400        85.0     70.1  
   640x400        85.1  
   640x350        85.1  
DVI-0 disconnected (normal left inverted right x axis y axis)


2) Radeon 3450 details ---------------------------------------------------------------------------
HIS HD 3450 Silence 512 Mb
http://germany.hisdigital.com/html/product_sp.php?id=366
# lspci -v
01:00.0 VGA compatible controller: ATI Technologies Inc Mobility Radeon HD 3450 (prog-if 00 [VGA controller])
	Subsystem: Hightech Information System Ltd. Device 2002
	Flags: bus master, fast devsel, latency 0, IRQ 11
	Memory at e0000000 (64-bit, prefetchable) [size=256M]
	Memory at f5000000 (64-bit, non-prefetchable) [size=64K]
	I/O ports at b000 [size=256]
	[virtual] Expansion ROM at f4000000 [disabled] [size=128K]
	Capabilities: [50] Power Management version 3
	Capabilities: [58] Express Legacy Endpoint, MSI 00
	Capabilities: [a0] Message Signalled Interrupts: Mask- 64bit+ Queue=0/0 Enable-
	Capabilities: [100] Vendor Specific Information <?>


3) dell 3008WFP details --------------------------------------------------------------------------
http://support.euro.dell.com/support/edocs/monitors/3008WFP/en/UG/index.htm

4) xorg.conf  ------------------------------------------------------------------------------------
Attached file xorg.conf_sid6.9.0-1+lenny4_1920x1440_work.txt

5) Xorg.0.log after setting xorg.conf to radeon and 2560x1600 with radeon git of 02-Nov-2008 -----
Attached file Xorg.0.log_git_081102_2560x1600_black_screen.txt