how to setup multiple ati gpus on ubuntu 12.04??

[joshpunb]

I need to do a fresh install on my machine and set it up for opencl programming and am having difficulties getting opencl to detect more than one ati gpus. I have three hd 6950 gpus installed as shown here:

$ lspci | grep VGA
01:00.0 VGA compatible controller: ATI Technologies Inc Cayman PRO [AMD Radeon 6900 Series]
06:00.0 VGA compatible controller: ATI Technologies Inc Cayman PRO [AMD Radeon 6900 Series]
07:00.0 VGA compatible controller: ATI Technologies Inc Cayman PRO [AMD Radeon 6900 Series]

Running opencl code to detect all available devices results in the following output:

CL_PLATFORM_NAME = AMD Accelerated Parallel Processing
CL_PLATFORM_VERSION = OpenCL 1.2 AMD-APP (938.1)
2 devices found
Device #0 name = Cayman
	Driver version = CAL 1.4.1741
	Global Memory (MB):	1024
	Global Memory Cache (MB):	0
	Local Memory (KB):	32
	Max clock (MHz) :	800
	Max Work Group Size:	256
	Number of parallel compute cores:	22
Device #1 name = AMD Phenom(tm) II X6 1090T Processor
	Driver version = 2.0 (sse2)
	Global Memory (MB):	16067
	Global Memory Cache (MB):	0
	Local Memory (KB):	32
	Max clock (MHz) :	800
	Max Work Group Size:	1024
	Number of parallel compute cores:	6

Is there something that I need to configure in xorg.conf to allow all devices to be seen by opencl?

Any help is greatly appreciated, as I haven't seen any other threads with the same problem that I am having with multiple ati gpus. I need to use linux for the OS (preferably ubuntu 12.04), but if someone else has had better luck on a different system, then I will consider changing the OS.

[RussianNeuroMancer]

If you already use OpenCL SDK 2.7, I suggest you go to AMD Developers forums http://devgurus.amd.com/welcome or contact with tech. support http://emailcustomercare.amd.com.