Yes, you have to disable SLI and extent the desktop. You also seemto have to have a monitor plugged in or at least a dummy plug.
the most I could get with the above is 3 running. Then I found the following registry hack. Works very well. What I have found so far is that I cannot overclock to the value I did before. Have not expermented much - been away a bit - but every few minuted, the screen would flicker and the WU would error out.
Okay the 4th GPU has entered the building.
After I taught myself CUDA I wrote my own program to enumerate the CUDA drivers present and was seeing 3 even though the nVidia control panel and the MMC device panel was showing 4. So it's not BOINC Manager.
I deinstalled all the nVidia drivers, rebooted and checked in the registry at
Hkey_Local_Machine\Hardware\DeviceMap\Video
to see what I had. There were 3 devices Video0, Video1 and Video2 present which were all standard VGA drivers. I then installed Forceware 185.68 and rebooted.
I now had 10 devices in the registry. I navigated down to
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video
and looked to see what was present. Here we see a list of registry keys like
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video\(GPU ID)\0000
where there is a key for each GPU. I searched the list and for each GPU e.g.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video\{D82C4D9A-396A-4292-A538-A8F8F22FFEB5}\0000\Settings field (where {D82C4D9A-396A-4292-A538-A8F8F22FFEB5} is a GPU id)
and looked for the words NVIDIA GeForce GTX 295.
I presumed (luckily correctly) that the 1st GPUID with those words in the Settings field had the monitor on it. To the following 3 GPU's I added the following registry keys:-
DisplayLessPolicy DWORD 1
LimitVideoPresentSources DWORD 1
at the
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video\(GPU ID)\0000
level in the registry tree and rebooted.
Now I only have 2 monitors showing in the nVidia control panel as having my desktop on them but my own CUDA program shows 4 GPUS. I fired up BOINC Manager which still displays that it found only 3 (due to the string length being exceeded I expect) but I have 4 running GPUS. 17) Message boards : Nvidia graphics cards (GPU) : Dual 295's only showing 3 of 4 cards (Message 8479)
Posted 10 days ago by JockMacMad TSBT
The abover works like a charm and not much work involved.