Previously, I had thought that this was a problem with OS/driver interaction, but it appears that others have managed to get this to work, hence this thread.

I have an X1950 Pro, using fully updated Ubuntu Feisty 64-bit.

With both the 8.41.7 and the 8.42.3 drivers, the highest resolution they claim to support is 1280x2253, although the 8.41.7 driver appears to detect other, larger, supported video modes from the EDID from my LCD monitor.
(My monitor's native resolution is 1440x900@60Hz)

Interestingly, if I try to install the 8.40.4 drivers, I get a black screen on boot, but my monitor claims that it is being driven at 1440x900@59Hz. Hence, the 8.40.4 drivers are /trying/ to get things to work, but failing for some reason.

My Xorg.0.log (from 8.41.7, since 8.42.3 introduces other problems for me) includes:

Code:
(--) PCI:*(2:0:0) ATI Technologies Inc ATI Radeon X1950 Pro Primary (PCIE) rev 154, Mem @ 0xd0000000/28, 0xfbce0000/16, I/O @ 0xd000/8, BIOS @ 0xfbcc0000/17
(--) PCI: (2:0:1) ATI Technologies Inc ATI Radeon X1950 Pro Secondary (PCIE) rev 154, Mem @ 0xfbcf0000/16
Code:
(II) fglrx(0): Connected Display1: CRT on primary DAC [crt1]
(II) fglrx(0): Display1 EDID data ---------------------------
(II) fglrx(0): Manufacturer: HSD  Model: b020  Serial#: 8647
(II) fglrx(0): Year: 2006  Week: 51
(II) fglrx(0): EDID Version: 1.3
(II) fglrx(0): Analog Display Input,  Input Voltage Level: 0.700/0.700 V
(II) fglrx(0): Sync:  Separate
(II) fglrx(0): Max H-Image Size [cm]: horiz.: 40  vert.: 25
(II) fglrx(0): Gamma: 2.20
(II) fglrx(0): DPMS capabilities: Off; RGB/Color Display
(II) fglrx(0): First detailed timing is preferred mode
(II) fglrx(0): redX: 0.644 redY: 0.327   greenX: 0.289 greenY: 0.613
(II) fglrx(0): blueX: 0.142 blueY: 0.078   whiteX: 0.310 whiteY: 0.340
(II) fglrx(0): Supported VESA Video Modes:
(II) fglrx(0): 720x400@70Hz
(II) fglrx(0): 640x480@60Hz
(II) fglrx(0): 640x480@67Hz
(II) fglrx(0): 640x480@72Hz
(II) fglrx(0): 640x480@75Hz
(II) fglrx(0): 800x600@56Hz
(II) fglrx(0): 800x600@60Hz
(II) fglrx(0): 800x600@72Hz
(II) fglrx(0): 800x600@75Hz
(II) fglrx(0): 832x624@75Hz
(II) fglrx(0): 1024x768@60Hz
(II) fglrx(0): 1024x768@70Hz
(II) fglrx(0): 1024x768@75Hz
(II) fglrx(0): 1280x1024@75Hz
(II) fglrx(0): 1152x870@75Hz
(II) fglrx(0): Manufacturer's mask: 0
(II) fglrx(0): Supported Future Video Modes:
(II) fglrx(0): #0: hsize: 1024  vsize 768  refresh: 66  vid: 18017
(II) fglrx(0): #1: hsize: 1152  vsize 864  refresh: 75  vid: 20337
(II) fglrx(0): #2: hsize: 1280  vsize 720  refresh: 60  vid: 49281
(II) fglrx(0): #3: hsize: 1280  vsize 1024  refresh: 60  vid: 32897
(II) fglrx(0): #4: hsize: 1400  vsize 1050  refresh: 60  vid: 16528
(II) fglrx(0): #5: hsize: 1400  vsize 1050  refresh: 75  vid: 20368
(II) fglrx(0): #6: hsize: 1440  vsize 900  refresh: 60  vid: 149
(II) fglrx(0): #7: hsize: 1440  vsize 900  refresh: 75  vid: 3989
(II) fglrx(0): Supported additional Video Mode:
(II) fglrx(0): clock: 106.5 MHz   Image Size:  408 x 255 mm
(II) fglrx(0): h_active: 1440  h_sync: 1520  h_sync_end 1672 h_blank_end 1904 h_border: 0
(II) fglrx(0): v_active: 900  v_sync: 903  v_sync_end 909 v_blanking: 934 v_border: 0
(II) fglrx(0): Serial No: 651HW2BY08647
(II) fglrx(0): Ranges: V min: 55  V max: 75 Hz, H min: 30  H max: 83 kHz, PixClock max 140 MHz
(II) fglrx(0): Monitor name: AH191
(II) fglrx(0): EDID (in hex):
(II) fglrx(0): 	00ffffffffffff00226420b0c7210000
(II) fglrx(0): 	33100103682819782af044a4534a9d24
(II) fglrx(0): 	144f57bfef806146714f81c081809040
(II) fglrx(0): 	904f9500950f9a29a0d0518422305098
(II) fglrx(0): 	360098ff1000001c000000ff00363531
(II) fglrx(0): 	48573242593038363437000000fd0037
(II) fglrx(0): 	4b1e530e000a202020202020000000fc
(II) fglrx(0): 	0041483139310a20202020202020006a
(II) fglrx(0): End of Display1 EDID data --------------------
(WW) fglrx(0): Only one display is connnected,so single mode is enabled
(II) fglrx(0): Primary Controller - CRT on primary DAC
(II) fglrx(0): Internal Desktop Setting: 0x00000001
(II) fglrx(0): POWERplay version 3.  1 power state available:
(II) fglrx(0):   1. 574/689MHz @ 0Hz [enable load balancing]
(==) fglrx(0): Qbs disabled
(==) fglrx(0): FAST_SWAP disabled
(==) fglrx(0):  PseudoColor visuals disabled
(==) fglrx(0): Using gamma correction (1.0, 1.0, 1.0)
(==) fglrx(0): Center Mode is disabled 
(==) fglrx(0): TMDS coherent mode is enabled 
(II) fglrx(0): Total of 26 modes found for primary display.
(--) fglrx(0): Virtual size is 1280x1024 (pitch 0)
(**) fglrx(0): *Mode "1280x1024": 135.0 MHz (scaled from 0.0 MHz), 80.0 kHz, 75.0 Hz
(II) fglrx(0): Modeline "1280x1024"  135.00  1280 1296 1440 1688  1024 1025 1028 1066
(**) fglrx(0):  Default mode "1280x1024": 108.0 MHz (scaled from 0.0 MHz), 64.0 kHz, 60.0 Hz
Does anyone have any ideas? Anyone with an X1950 Pro running in 1440x900 properly, for example?

(If I force 1440x900 by altering my xorg.conf to include an explicit modeline based on that in the Xorg.0.log, and then switch to it, I get a corrupted display at 1440x900, but with everything outside 1280x900 mirrored in strips either side of the display.

That is, it looks like this:

XOOOOOX
XOOOOOX
XOOOOOX

where the XOOOOO block is 1280, the OOOOOX block is also 1280 and the full width is 1440x900, and the Xs both contain the same vertical strip - which is a messed up combination of the far left and far right sides of the display. This is, of course, unusable.)