Insufficient available DisplayPort bandwidth for 8 4K monitors


I’m trying to create configuration with eight 4K monitors as separate screens using two PNY T1000 4Gb video cards, but found that it can drive only 6 monitors at 3480x2150@60 and failed on seventh monitor:

39858 [ 12066.991] (II) NVIDIA(6): kernel module enabled successfully
39859 [ 12066.991] (II) NVIDIA(6): GPU initialized
39860 [ 12066.992] (==) NVIDIA(6): Using 8388608 bytes for software rendering cache
39861 [ 12067.005] (II) NVIDIA(6): Setting mode "DFP-6:3840x2160"
39862 [ 12067.006] (WW) NVIDIA(6): Failed to set the display configuration
39863 [ 12067.006] (WW) NVIDIA(6):  - Setting a mode on display 0 failed: There was insufficient
39864 [ 12067.006] (WW) NVIDIA(6):     available DisplayPort bandwidth
39865 [ 12067.006] (EE)
39866 Fatal server error:
39867 [ 12067.006] (EE) AddScreen/ScreenInit failed for driver 6

Datasheet for T1000 states that it supports 4x 3840 x 2160 @ 120Hz.

How to fix this absence of bandwidth?

nvidia-bug-report.log.gz (1.6 MB)
Xorg.0.log.tgz (169.2 KB)
xorg.conf (11.2 KB)

Does that monitor still fail to set that mode if it’s the only one connected? DisplayPort negotiates the available bandwidth using an active handshake with the sink device, so it’s possible that the monitor itself, the cable, or the port on the GPU is limiting it. I would recommend swapping around monitors, cables, and ports to identify exactly which is the limiting factor here.

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I’m continue investigating with 8 identical plugs. Was able to create 2 screens each of 4 monitors of resolution 3840x2160 @ 60Hz, but when I try to build 8 separate 4K screens - again run into error about bandwidth or another one:

39970 [   974.145] (II) NVIDIA(7): kernel module enabled successfully
39971 [   974.145] (II) NVIDIA(7): GPU initialized
39972 [   974.147] (==) NVIDIA(7): Using 8388608 bytes for software rendering cache
39973 [   974.160] (II) NVIDIA(7): Setting mode "DFP-4:3840x2160"
39974 [   974.188] (WW) NVIDIA(7): Failed to set the display configuration
39975 [   974.188] (WW) NVIDIA(7):  - Setting a mode on head 3 failed: Invalid surface parameters
39976 [   974.188] (WW) NVIDIA(7):     were specified
39977 [   974.188] (EE)
39978 Fatal server error:
39979 [   974.188] (EE) AddScreen/ScreenInit failed for driver 7

After building configuration from scratch with nvidia-settings and saving it into xorg.conf I can’t start this configuration.

Interesting, thanks. That’s a different error and kind of surprising. Can you generate and attach a bug report log from that configuration too?

I’m also kind of curious whether this is specific to 8 separate X screens or if the problem also occurs if you have two X screens with four displays each. Would you mind giving that a try, if possible?

At the moment I can’t reproduce that new error - I switched to configuration with only one T1000 card.

But even in such ordinary configuration I can’t have 4 separate screens with 4K monitors - same error as initially - There was insufficient available DisplayPort bandwidth - and it seems like error appeared on output three. According to T1000 specification it can do 4K@120 Hz on each output - seems like driver count those lines for two 4K channels at 60Hz and then reports that no lines left. But it must use lines from each separate output when separate screens are configured?

Here is bug report for this configuration - but now I’m really don’t know what else to try - older driver or more recent Linux (Ubuntu 23) version?

This seems like fundamental problem now with even single T1000.

nvidia-bug-report.log.gz (619.9 KB)

So inability to create four separate screens on one T1000 video card must be driver error? Or information about support of four 4K@120Hz were false advertising for T1000? At least not for Linux? It would be nice to have some sort of official confirmation that such configuration is not possible…

I returned to similar task, now with 3 T1000 8Gb video cards. Now with driver 535.54.03 and I still can’t create configuration with 4 4K@60Hz separate Screens. Only 3 4K@60Hz Screens allowed, if forth is added than “Invalid surface parameters” immediately appeared in log and no graphics started.

I tried this and all work fine when I had two X screens with four displays each. In such configuration I can have 4K@60Hz for each monitor. Same now with 3 video cards - having three X screens I can run all 12 monitors at 4K@60Hz, but when I start to create separate screens then only 3 screens are working.