Multi-head on a 9800 GX2

[mattty]

I am trying to get multihead to work on a 9800 GX2 in an Ubuntu 8.04 box.

The GX2 is two gpus inside of one card. To lspci and all the other tools, it appears that I have two cards in my system.

Using nvidia-settings, I made an xorg.conf to try and run X across both gpus. Sadly, it does not seem to work for me. I have tried with and without Xinerama.

What happens is that the system sits for a long time at the Nvidia logo that is displayed when X starts. After a few minutes, the primary gpu (which runs great under normal conditions) continues into X while the other gpu still shows the logo.

The primary gpu does not get very far into X -- the gdm greeter does not finish drawing itself. I can move the mouse, but otherwise not interact with the system. Can't do ctrl-alt-back or switch to a VT. Ssh'ing into the system and running top shows X using 100% cpu, presumably busy-waiting for the other gpu.

Interestingly, this seems to be the same outcome as if I try the MultiGPU option (which I guess is just SLI on the card, right?)

I hope you guys can help me find a solution. I'm working on a project right now that will rely pretty heavily on this working (we want to take it up to three GX2s -> 6 video outputs.) It has occurred to me that I could stand to update my motherboard bios, but I have not gotten around to that.

Thanks!

[JaXXoN]

I'm pretty sure your problems are related to this output in xorg.conf:

(WW) NVIDIA(1): WAIT (0, 6, 0x8000, 0x00000870, 0x00000870)
[...]
(WW) NVIDIA(1): WAIT (2, 6, 0x8000, 0x00000b18, 0x00001b4c)
(WW) NVIDIA(1): WAIT (1, 6, 0x8000, 0x00000b18, 0x00001b4c)

This is a typical sign that there is some sort of hardware incompatibility,
but it might be possible to overcome this in software. I recommend
performing the BIOS update and/or trying out the pre and/or beta
releases of the nvidia driver.

regards

Bernhard

[mattty]

I noticed the waits, but forgot to mention them. I googled around but did not find anything conclusive. It occured to me that *maybe* I have a bad card, because I essentially have never booted the 2nd gpu.

I have another GX2 I can try.

*SOMEONE* has had GX2s (of some variety) work in Linux before, with both gpus, right?

[JaXXoN]

Originally Posted by mattty

*SOMEONE* has had GX2s (of some variety) work in Linux before, with both gpus, right?

Using the search function of this forum for "GX2" reveals a small number of
success reports, i.e. this one:

http://www.nvnews.net/vbulletin/showthread.php?t=115089

regards

Bernhard

[mattty]

Hrmm. My xorg.conf is very similar to his, but I am not trying to use twinview. I don't think twinview is even supposed to work since there is only one dvi output per gpu on these cards (unless I am mistaken).

I guess I will research some of these other threads. I searched before, but I mixed other search terms in and did not get anything that was very helpful.

[JaXXoN]

Originally Posted by mattty

Hrmm. My xorg.conf is very similar to his, but I am not trying to use twinview.

I was referring to the xorg.conf in posting #4 in the thread linked, above.
There, two devices are defined and xinerama is enabled (no twinview).
Sorry for the potential confusion.

Originally Posted by mattty

I don't think twinview is even supposed to work since there is only one dvi output per gpu on these cards (unless I am mistaken).

This is my understanding of the GX2, as well. I think your xorg.conf is fine.
As far as i understand, there is typically not a common method to get rid of
those "WAIT" messages - you need to experiment. BTW.: Is the GX2 working
fine in a PC with a different mainboard?

regards

Bernhard

[mattty]

I do not have another PC with pcie slots right now, but it is an option. I would need to go borrow one.

Is there an official list of what the WAIT messages could be, or is it just considered to be some kind of hardware compatibility issue?

I still need to update my bios. It is an Abit 680i board that is a few bios versions behind, so it is not unreasonable that there might be a bug there.

[JaXXoN]

I'm not aware of that there exists anything "official".

If you search for "(WW) NVIDIA(0): WAIT" i.e. on google, you may stumble
over the solution. For example, somebody suggested to disable "UseEvents".

http://www.nvnews.net/vbulletin/showthread.php?t=86253

regards

Bernhard

[mattty]

Well, I tried all these options and it did not work.

Then I tried a different GX2 and removing all my pci cards. Now it works!

I put the prior GX2 in, and it hangs again. So I guess I may have a bad card. I'm about to go confirm it after this post. I kind of wish Nvidia's driver could have given me a more informative message, but who can say that the nature of this failure would have been helpful for that.

[mattty]

So now I am finding that the RANDR extension goes away when I configure two gpus. Is this expected?

/var/log/Xorg.conf only says that RANDR initializes ok, but it is not available when I invoke any tools.

Non-twinview multimonitor support looks like a very sad situation at the moment

[JaXXoN]

Originally Posted by mattty

So now I am finding that the RANDR extension goes away when I configure two gpus. Is this expected?

Unfortunately, yes.

Originally Posted by mattty

Non-twinview multimonitor support looks like a very sad situation at the moment

Depending on what you try to achive, multi-GPU may work ok.

But if you want to avoid a lot of headache, i recommend the
following alternatives for triple head and/or up to six head setups:

http://www.nvnews.net/vbulletin/showthread.php?t=106517
http://www.nvnews.net/vbulletin/showthread.php?t=126134

However, those solutions cost some money ...

regards

Bernhard

[mattty]

I think xgl is my best bet right now: http://meandubuntu.wordpress.com/200...ama-on-nvidia/

I was hoping to use RANDR, but that idea died quick. The dualhead2go won't work for me because I'm ultimately wanting to span 6 gpus (well, 6 displays in total.. but at best, that still takes 2-3 gpus).