GTX 295, CUDA thinks I have only 30 multiprocessors

Accelerated Computing CUDA CUDA Programming and Performance
1

I have a single GTX 295 card installed on to a Rampage II extreme board, 12 GB RAM, i7 965 CPU, and I am running Vista x64.

When I compile & run the ‘deviceQuery’ project included with the CUDA SDK samples, I get the following output:

There is 1 device supporting CUDA

Device 0: "GeForce GTX 295"
Major revision number: 1
Minor revision number: 3
Total amount of global memory: 939524096 bytes
Number of multiprocessors: 30
Number of cores: 240
Total amount of constant memory: 65536 bytes
Total amount of shared memory per block: 16384 bytes
Total number of registers available per block: 16384
Warp size: 32
Maximum number of threads per block: 512
Maximum sizes of each dimension of a block: 512 x 512 x 64
Maximum sizes of each dimension of a grid: 65535 x 65535 x 1
Maximum memory pitch: 262144 bytes
Texture alignment: 256 bytes
Clock rate: 1.24 GHz
Concurrent copy and execution: No

Test PASSED

Press ENTER to exit...

I was expecting that CUDA would ‘see’ 2 cards with 30 MPs each, or possible 1 card with 60 MPs (either way, a total of 480 cores).

This would suggest that the CUDA code I write cannot take full advantage of the GTX 295.

How can I ‘see’ the full resources of the GTX 295? External Media

2

It’s likely you have SLI enabled. You need to disable it to make it appear as two devices to CUDA.

You will never see 1 device with 60MPs.

3

You need to:

  1. Disable multi-GPU mode (Nvidia control panel)
  2. Plug in monitors: one into the HDMI port and one of the DVI ports.

See for earlier discussions;
[url=“http://forums.nvidia.com/index.php?showtopic=89002”]http://forums.nvidia.com/index.php?showtopic=89002[/url]

4

tmurray posted a registry hack in the Vista forums a couple weeks ago that negates the need to plug a monitor into each port:

http://forums.nvidia.com/index.php?s=&…st&p=517428

5

not really a hack, it’s what the driver control panel actually sets–there’s just not a good UI for it yet.

6

Sorry, poor choice of wording on my part.