My C870 now has a default monitor


I just installed the GeForce driver package 182.08, which installes GeForce driver version on my 8800GTX card. The C870 driver version is still In my Vista 32 system, I now notice that Vista shows a default monitor device on my Tesla C870 card. I find this weird because the C870 card does not have a monitor output. At least I have not seen it :)

Has anyone else observe this? Is there a reason for this default monitor?


As I understand it, Vista considers GPUs without monitors to be utterly useless and won’t even let the drivers access them. NVIDIA’s drivers therefore must fake a monitor on Tesla cards in order for them to be usable.

That’s wierd. I have a couple of systems running Server 2008 with GPUs with no montors attached, and it detects them easily. Could it be a Vista-only limitation?

Here’s the secret sauce for enabling CUDA on non-display cards in Vista or Server 2008 using 18x.xx drivers. It’s what the PhysX control panel does for one card (sort of, I think this is more thorough and also makes the card show up as no timeout enabled? but you still need to disable the TDR timeout to make that work correctly, I think):

  • In the registry, go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video(GPU ID)\0000 (you might also have to hit 0001 on a D870 or Plex D2)
  • add the following two DWORDs and set them to 1:


  • reboot.

I don’t know of a good way to look up GPU IDs, so look at the name entries in each to figure out what you should be touching.

Strange - on my system LimitVideoPresentSources already exists, but is a REG_BINARY. What’s with that?

I’ve seen that too, it might be how the PhysX control panel creates it.


I have tried this on Windows 7 x64 with one GTX 295, but only one core is known to Cuda, despite 2 are known to the operating system/Nvidia.


Anybody figured out how to lookup GPUID’s?

I have a system with only one GPU a 9800gt, but I cant figure out what registry value to edit, because there are so many GPUID’s under Video?
Also do you need to extend the desktop for this to work?

In my UNEDITED Registry “LimitVideoPresentSources” is a binary value “01 00 00 00” at the 0000 level, and, “DisplayLessPolicy” was found at the {GPUID} parent level. I’m running 186.18 drivers. Do you know why “DisplayLessPolicy” appears at at a location other than what you specify or why “LimitVideoPresentSources” is a binary value rather than a DWORD? Is there any documentation on what these do specifically? (I’m trying to troubleshoot a related issue with 4 x GTX-295 in a benchmark config)

I am seeing the same values in my Win7 x64 System.

I am using driver 191.07.

It is interesting that in Win7, the GUID key does not seem to be generated unless a monitor has been attached to the port.

Has anyone been able to workthrough this?

    • Silveradocyn

can you activate it and extend a fake desktop to it? I did that once with Win7 (screen resolution -> detect -> display VGA? something like that), so I think that might work if it actually doesn’t generate the GUID section (which seems weird, that should be generated at driver install time).