[alex31]

In fact, the ibm t221 screen has two dvi entries, one dual link which addresses 2/3 of the screen (2624x2400) and one single link which addresses 1/3 oh the screen (1216x2400), so from the graphic card it is seen as two screens.

In fact it's a litte more complex, you can adresses all the screen (3840x2400) with just one double dvi link, but in this case you are limited @ 24hz. If you want to use the screen at his top freq (48hz) you need to use the 2 dvi entries.

Since it do not work anymore with 8x.xx drivers, i have done several trials, and the last time i have tried, i have, like you have detected, inverted the 2624 entry and the 1216 one, putting the 2624 on the single link side.

I hace corrected this error and lauched again with -logverbose 6

But even with the good combination, it still fail.
(--) NVIDIA(0): DFP-0: maximum pixel clock: 310 MHz
(--) NVIDIA(0): DFP-0: Internal Dual Link TMDS
(II) NVIDIA(0): Mapping display device 1 (DFP-1) to CRTC 1
(--) NVIDIA(0): DFP-1: maximum pixel clock: 310 MHz
(--) NVIDIA(0): DFP-1: Internal Single Link TMDS


(II) NVIDIA(0): Adding EDID-provided mode "3840x2400" for DFP-0.
(II) NVIDIA(0): Adding EDID-provided mode "2624x2400" for DFP-0.
(II) NVIDIA(0): Adding EDID-provided mode "1216x2400" for DFP-0.
(II) NVIDIA(0): Adding EDID-provided mode "1920x1200" for DFP-0.
(II) NVIDIA(0): Frequency information for DFP-1:
(II) NVIDIA(0): HorizSync : 31.500-160.000 kHz
(II) NVIDIA(0): VertRefresh : 19.000-62.000 Hz
(II) NVIDIA(0): (HorizSync from SecondMonitorHorizSync X Config Option)
(II) NVIDIA(0): (VertRefresh from SecondMonitorVertRefresh X Config
(II) NVIDIA(0): Option)
(II) NVIDIA(0): Adding EDID-provided mode "3840x2400" for DFP-1.
(II) NVIDIA(0): Adding EDID-provided mode "2624x2400" for DFP-1.
(II) NVIDIA(0): Adding EDID-provided mode "1216x2400" for DFP-1.
(II) NVIDIA(0): Adding EDID-provided mode "1920x1200" for DFP-1.
(II) NVIDIA(0): Parsed 1 valid MetaMode(s)
(II) NVIDIA(0): MetaMode [0]; display [0]; name : "2624x2400"
(II) NVIDIA(0): MetaMode [0]; display [1]; name : "1216x2400"

At this stage each screen is correctly detected,a and EDID mode are read.

(II) NVIDIA(0): Clock range: 12.00 to 310.00 MHz
(II) NVIDIA(0): Not using default mode "1024x768" (vrefresh out of range)
(II) NVIDIA(0): Not using default mode "512x384" (vrefresh out of range)
(II) NVIDIA(0): Not using default mode "1920x1440" (bad mode clock/interlace/doublescan)
(II) NVIDIA(0): Not using default mode "960x720" (hsync out of range)
(II) NVIDIA(0): Not using default mode "2048x1536" (bad mode clock/interlace/doublescan)
(II) NVIDIA(0): Not using default mode "1024x768" (hsync out of range)
(II) NVIDIA(0): Not using default mode "2048x1536" (bad mode clock/interlace/doublescan)
(II) NVIDIA(0): Not using default mode "1024x768" (hsync out of range)
(II) NVIDIA(0): Not using mode "2624x2400" (bad mode clock/interlace/doublescan)
(II) NVIDIA(0): Not using mode "" (bad mode clock/interlace/doublescan)

But here, 2624x2400 mode is rejected by 8x.xx driver, in the 7x.xx serie of driver this mode was accepted.
I join the entire nvidia-bug-report.log.zip

As usual, thanks for any help !
Alexandre