4 x GTX-295: CUDA only sees 5 x GPU (NOT the usual issues!)

(Cross Posted to CUDA/Vista)

I have been benchmarking various CUDA configurations on an ASUS P6T7 WS Motherboard. This includes configurations consisting of the following cards: 9600GT, GTX-295, Quadro FX5800, and three Tesla C1060 cards. Everything seems to work as expected except when I have multiple GTX-295 cards in the system. I am running Vista Ultimate 64 SP2 and using the 186.18 drivers.

For the 4 x GTX-295 config: The Device Manager see’s all 8 GPU’s. GPU-Z sees all 8 GPU’s. However the CUDA Apps I am using (BOINC and EDPR) only report 5 GPU’s in the system. Through several reconfigurations it appears that the primary video card is getting credit for two GPU’s and the rest only get 1 per card. (IOW. 2 cards present 3 GPU’s, 3 cards present 4 GPU’s, 4 cards present 5 GPU’s).

I have PhysX enabled and SLI disabled.

I have monitors attached to all video ports on all cards and the desktop is spread across all of them. (A KVM works nicely for this - I can see all desktops independently without actually needing multiple monitors)

I have also tried the “LimitVideoPresent Sources” and “DisplayLessPolicy” registry updates and this makes no difference… (Although in my initial (unedited) registry, the “DisplayLessPolicy” was not at the 0000 or 0001 level but rather just under the GPUID key. “LimitVideoPresent” was at the 0000 level however in the unedited registry and was a binary entry - not DWORD). In any case, I don’t think this really matters if I have all 8 monitors hooked up…

My current config in focus is only 2xGTX-295 (which only presents 3 GPU’s). I don’t see any point in messing with 3 or 4 cards until I get two properly presented…

Anyone have a clue? I spent most of the day yesterday searching the web for helpful info… Could this be a 186.18 driver issue? I also had Tesla cards in the system at one point - could they have “poisoned” the registry and limited functionality of any replacement cards in their positions?

Although I did reinstall the box once already to try and diagnose this issue, I am in the process of a fresh install again to clear the decks…

Thanks in advance,