I can pick only 3 OpenCL devices

[tynt]

I was running 2x5970 + 2*6870, which makes total of 6 GPUs, everything was fine.
I added another 6870 and everything seems to be fine, all 7 GPUs are recognized but I can't run cgminer unless I pick only 3 of them and disable others.
Otherwise I get this errormessage:

Error -6: Creating Command Queue. (clCreateCommandQueue)
Try to disable device 3
...

I can pick only 3 devices, doesnt matter which of them. I lowered number of gpu threads in cgminer (--gpu-threads 1).
Now I can pick 5 devices, but not more.

What gives? Bug in App SDK?

Windows 7 64bit
Catalyst 11.12, SDK 2.5
MSI 790FXA-GD70
2000W PSU
10GB ram

Edit: More specs

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[-ck]

Error number -6 :
#define CL_OUT_OF_HOST_MEMORY                       -6

[tynt]

I use 64bit Windows and 10GB ram.
And cards I use: 2*5970 + 2*6870 + 5870
Tried different kernels, same problem.

There is no limit on the number of commands in a commandqueue. It is only restricted by the system memory.

If you exceed this limit you are likely to get a CL_OUT_OF_HOST_MEMORY.

I hope it is clear

If HOST_MEMORY means RAM then I'll try 16GB of it.

EDIT: I realised I use 32bit version of cgminer. Does it make sense if I try to compile 64bit version of it?

[ssateneth]

I use 64bit Windows and 10GB ram.
And cards I use: 2*5970 + 2*6870 + 5870
Tried different kernels, same problem.

There is no limit on the number of commands in a commandqueue. It is only restricted by the system memory.

If you exceed this limit you are likely to get a CL_OUT_OF_HOST_MEMORY.

I hope it is clear

If HOST_MEMORY means RAM then I'll try 16GB of it.

EDIT: I realised I use 32bit version of cgminer. Does it make sense if I try to compile 64bit version of it?

You have a lot of GPU devices. You will probably need to disable certain system devices in the BIOS such as serial/parallel port, USB ports, audio, PS/2 support, and so on to make room for the GPU's to be mapped.

[ionbasa]

I use 64bit Windows and 10GB ram.
And cards I use: 2*5970 + 2*6870 + 5870
Tried different kernels, same problem.

There is no limit on the number of commands in a commandqueue. It is only restricted by the system memory.

If you exceed this limit you are likely to get a CL_OUT_OF_HOST_MEMORY.

I hope it is clear

If HOST_MEMORY means RAM then I'll try 16GB of it.

EDIT: I realised I use 32bit version of cgminer. Does it make sense if I try to compile 64bit version of it?

http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778(v=vs.85).aspx
You need to compile the 64 bit version of cgminer otherwise you run into a memory issue with Windows.